(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.adapter = f()}})(function(){var define,module,exports;return (function(){function r(e,n,t){function o(i,f){if(!n[i]){if(!e[i]){var c="function"==typeof require&&require;if(!f&&c)return c(i,!0);if(u)return u(i,!0);var a=new Error("Cannot find module '"+i+"'");throw a.code="MODULE_NOT_FOUND",a}var p=n[i]={exports:{}};e[i][0].call(p.exports,function(r){var n=e[i][1][r];return o(n||r)},p,p.exports,r,e,n,t)}return n[i].exports}for(var u="function"==typeof require&&require,i=0;i<t.length;i++)o(t[i]);return o}return r})()({1:[function(require,module,exports){
        /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */

        'use strict';

        var _adapter_factory = require('./adapter_factory.js');

        var adapter = (0, _adapter_factory.adapterFactory)({ window: typeof window === 'undefined' ? undefined : window });
        module.exports = adapter; // this is the difference from adapter_core.

    },{"./adapter_factory.js":2}],2:[function(require,module,exports){
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });
        exports.adapterFactory = adapterFactory;

        var _utils = require('./utils');

        var utils = _interopRequireWildcard(_utils);

        var _chrome_shim = require('./chrome/chrome_shim');

        var chromeShim = _interopRequireWildcard(_chrome_shim);

        var _edge_shim = require('./edge/edge_shim');

        var edgeShim = _interopRequireWildcard(_edge_shim);

        var _firefox_shim = require('./firefox/firefox_shim');

        var firefoxShim = _interopRequireWildcard(_firefox_shim);

        var _safari_shim = require('./safari/safari_shim');

        var safariShim = _interopRequireWildcard(_safari_shim);

        var _common_shim = require('./common_shim');

        var commonShim = _interopRequireWildcard(_common_shim);

        function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

// Shimming starts here.
        /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        function adapterFactory() {
            var _ref = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {},
                window = _ref.window;

            var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {
                shimChrome: true,
                shimFirefox: true,
                shimEdge: true,
                shimSafari: true
            };

            // Utils.
            var logging = utils.log;
            var browserDetails = utils.detectBrowser(window);

            var adapter = {
                browserDetails: browserDetails,
                commonShim: commonShim,
                extractVersion: utils.extractVersion,
                disableLog: utils.disableLog,
                disableWarnings: utils.disableWarnings
            };

            // Shim browser if found.
            switch (browserDetails.browser) {
                case 'chrome':
                    if (!chromeShim || !chromeShim.shimPeerConnection || !options.shimChrome) {
                        logging('Chrome shim is not included in this adapter release.');
                        return adapter;
                    }
                    if (browserDetails.version === null) {
                        logging('Chrome shim can not determine version, not shimming.');
                        return adapter;
                    }
                    logging('adapter.js shimming chrome.');
                    // Export to the adapter global object visible in the browser.
                    adapter.browserShim = chromeShim;

                    chromeShim.shimGetUserMedia(window);
                    chromeShim.shimMediaStream(window);
                    chromeShim.shimPeerConnection(window);
                    chromeShim.shimOnTrack(window);
                    chromeShim.shimAddTrackRemoveTrack(window);
                    chromeShim.shimGetSendersWithDtmf(window);
                    chromeShim.shimGetStats(window);
                    chromeShim.shimSenderReceiverGetStats(window);
                    chromeShim.fixNegotiationNeeded(window);

                    commonShim.shimRTCIceCandidate(window);
                    commonShim.shimConnectionState(window);
                    commonShim.shimMaxMessageSize(window);
                    commonShim.shimSendThrowTypeError(window);
                    commonShim.removeAllowExtmapMixed(window);
                    break;
                case 'firefox':
                    if (!firefoxShim || !firefoxShim.shimPeerConnection || !options.shimFirefox) {
                        logging('Firefox shim is not included in this adapter release.');
                        return adapter;
                    }
                    logging('adapter.js shimming firefox.');
                    // Export to the adapter global object visible in the browser.
                    adapter.browserShim = firefoxShim;

                    firefoxShim.shimGetUserMedia(window);
                    firefoxShim.shimPeerConnection(window);
                    firefoxShim.shimOnTrack(window);
                    firefoxShim.shimRemoveStream(window);
                    firefoxShim.shimSenderGetStats(window);
                    firefoxShim.shimReceiverGetStats(window);
                    firefoxShim.shimRTCDataChannel(window);
                    firefoxShim.shimAddTransceiver(window);
                    firefoxShim.shimGetParameters(window);
                    firefoxShim.shimCreateOffer(window);
                    firefoxShim.shimCreateAnswer(window);

                    commonShim.shimRTCIceCandidate(window);
                    commonShim.shimConnectionState(window);
                    commonShim.shimMaxMessageSize(window);
                    commonShim.shimSendThrowTypeError(window);
                    break;
                case 'edge':
                    if (!edgeShim || !edgeShim.shimPeerConnection || !options.shimEdge) {
                        logging('MS edge shim is not included in this adapter release.');
                        return adapter;
                    }
                    logging('adapter.js shimming edge.');
                    // Export to the adapter global object visible in the browser.
                    adapter.browserShim = edgeShim;

                    edgeShim.shimGetUserMedia(window);
                    edgeShim.shimGetDisplayMedia(window);
                    edgeShim.shimPeerConnection(window);
                    edgeShim.shimReplaceTrack(window);

                    // the edge shim implements the full RTCIceCandidate object.

                    commonShim.shimMaxMessageSize(window);
                    commonShim.shimSendThrowTypeError(window);
                    break;
                case 'safari':
                    if (!safariShim || !options.shimSafari) {
                        logging('Safari shim is not included in this adapter release.');
                        return adapter;
                    }
                    logging('adapter.js shimming safari.');
                    // Export to the adapter global object visible in the browser.
                    adapter.browserShim = safariShim;

                    safariShim.shimRTCIceServerUrls(window);
                    safariShim.shimCreateOfferLegacy(window);
                    safariShim.shimCallbacksAPI(window);
                    safariShim.shimLocalStreamsAPI(window);
                    safariShim.shimRemoteStreamsAPI(window);
                    safariShim.shimTrackEventTransceiver(window);
                    safariShim.shimGetUserMedia(window);
                    safariShim.shimAudioContext(window);

                    commonShim.shimRTCIceCandidate(window);
                    commonShim.shimMaxMessageSize(window);
                    commonShim.shimSendThrowTypeError(window);
                    commonShim.removeAllowExtmapMixed(window);
                    break;
                default:
                    logging('Unsupported browser!');
                    break;
            }

            return adapter;
        }

// Browser shims.

    },{"./chrome/chrome_shim":3,"./common_shim":6,"./edge/edge_shim":7,"./firefox/firefox_shim":11,"./safari/safari_shim":14,"./utils":15}],3:[function(require,module,exports){
        /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });
        exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined;

        var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

        var _getusermedia = require('./getusermedia');

        Object.defineProperty(exports, 'shimGetUserMedia', {
            enumerable: true,
            get: function get() {
                return _getusermedia.shimGetUserMedia;
            }
        });

        var _getdisplaymedia = require('./getdisplaymedia');

        Object.defineProperty(exports, 'shimGetDisplayMedia', {
            enumerable: true,
            get: function get() {
                return _getdisplaymedia.shimGetDisplayMedia;
            }
        });
        exports.shimMediaStream = shimMediaStream;
        exports.shimOnTrack = shimOnTrack;
        exports.shimGetSendersWithDtmf = shimGetSendersWithDtmf;
        exports.shimGetStats = shimGetStats;
        exports.shimSenderReceiverGetStats = shimSenderReceiverGetStats;
        exports.shimAddTrackRemoveTrackWithNative = shimAddTrackRemoveTrackWithNative;
        exports.shimAddTrackRemoveTrack = shimAddTrackRemoveTrack;
        exports.shimPeerConnection = shimPeerConnection;
        exports.fixNegotiationNeeded = fixNegotiationNeeded;

        var _utils = require('../utils.js');

        var utils = _interopRequireWildcard(_utils);

        function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

        function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }

        function shimMediaStream(window) {
            window.MediaStream = window.MediaStream || window.webkitMediaStream;
        }

        function shimOnTrack(window) {
            if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && !('ontrack' in window.RTCPeerConnection.prototype)) {
                Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
                    get: function get() {
                        return this._ontrack;
                    },
                    set: function set(f) {
                        if (this._ontrack) {
                            this.removeEventListener('track', this._ontrack);
                        }
                        this.addEventListener('track', this._ontrack = f);
                    },

                    enumerable: true,
                    configurable: true
                });
                var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription;
                window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription() {
                    var _this = this;

                    if (!this._ontrackpoly) {
                        this._ontrackpoly = function (e) {
                            // onaddstream does not fire when a track is added to an existing
                            // stream. But stream.onaddtrack is implemented so we use that.
                            e.stream.addEventListener('addtrack', function (te) {
                                var receiver = void 0;
                                if (window.RTCPeerConnection.prototype.getReceivers) {
                                    receiver = _this.getReceivers().find(function (r) {
                                        return r.track && r.track.id === te.track.id;
                                    });
                                } else {
                                    receiver = { track: te.track };
                                }

                                var event = new Event('track');
                                event.track = te.track;
                                event.receiver = receiver;
                                event.transceiver = { receiver: receiver };
                                event.streams = [e.stream];
                                _this.dispatchEvent(event);
                            });
                            e.stream.getTracks().forEach(function (track) {
                                var receiver = void 0;
                                if (window.RTCPeerConnection.prototype.getReceivers) {
                                    receiver = _this.getReceivers().find(function (r) {
                                        return r.track && r.track.id === track.id;
                                    });
                                } else {
                                    receiver = { track: track };
                                }
                                var event = new Event('track');
                                event.track = track;
                                event.receiver = receiver;
                                event.transceiver = { receiver: receiver };
                                event.streams = [e.stream];
                                _this.dispatchEvent(event);
                            });
                        };
                        this.addEventListener('addstream', this._ontrackpoly);
                    }
                    return origSetRemoteDescription.apply(this, arguments);
                };
            } else {
                // even if RTCRtpTransceiver is in window, it is only used and
                // emitted in unified-plan. Unfortunately this means we need
                // to unconditionally wrap the event.
                utils.wrapPeerConnectionEvent(window, 'track', function (e) {
                    if (!e.transceiver) {
                        Object.defineProperty(e, 'transceiver', { value: { receiver: e.receiver } });
                    }
                    return e;
                });
            }
        }

        function shimGetSendersWithDtmf(window) {
            // Overrides addTrack/removeTrack, depends on shimAddTrackRemoveTrack.
            if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && !('getSenders' in window.RTCPeerConnection.prototype) && 'createDTMFSender' in window.RTCPeerConnection.prototype) {
                var shimSenderWithDtmf = function shimSenderWithDtmf(pc, track) {
                    return {
                        track: track,
                        get dtmf() {
                            if (this._dtmf === undefined) {
                                if (track.kind === 'audio') {
                                    this._dtmf = pc.createDTMFSender(track);
                                } else {
                                    this._dtmf = null;
                                }
                            }
                            return this._dtmf;
                        },
                        _pc: pc
                    };
                };

                // augment addTrack when getSenders is not available.
                if (!window.RTCPeerConnection.prototype.getSenders) {
                    window.RTCPeerConnection.prototype.getSenders = function getSenders() {
                        this._senders = this._senders || [];
                        return this._senders.slice(); // return a copy of the internal state.
                    };
                    var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
                    window.RTCPeerConnection.prototype.addTrack = function addTrack(track, stream) {
                        var sender = origAddTrack.apply(this, arguments);
                        if (!sender) {
                            sender = shimSenderWithDtmf(this, track);
                            this._senders.push(sender);
                        }
                        return sender;
                    };

                    var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
                    window.RTCPeerConnection.prototype.removeTrack = function removeTrack(sender) {
                        origRemoveTrack.apply(this, arguments);
                        var idx = this._senders.indexOf(sender);
                        if (idx !== -1) {
                            this._senders.splice(idx, 1);
                        }
                    };
                }
                var origAddStream = window.RTCPeerConnection.prototype.addStream;
                window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
                    var _this2 = this;

                    this._senders = this._senders || [];
                    origAddStream.apply(this, [stream]);
                    stream.getTracks().forEach(function (track) {
                        _this2._senders.push(shimSenderWithDtmf(_this2, track));
                    });
                };

                var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
                window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
                    var _this3 = this;

                    this._senders = this._senders || [];
                    origRemoveStream.apply(this, [stream]);

                    stream.getTracks().forEach(function (track) {
                        var sender = _this3._senders.find(function (s) {
                            return s.track === track;
                        });
                        if (sender) {
                            // remove sender
                            _this3._senders.splice(_this3._senders.indexOf(sender), 1);
                        }
                    });
                };
            } else if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && 'getSenders' in window.RTCPeerConnection.prototype && 'createDTMFSender' in window.RTCPeerConnection.prototype && window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
                var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
                window.RTCPeerConnection.prototype.getSenders = function getSenders() {
                    var _this4 = this;

                    var senders = origGetSenders.apply(this, []);
                    senders.forEach(function (sender) {
                        return sender._pc = _this4;
                    });
                    return senders;
                };

                Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
                    get: function get() {
                        if (this._dtmf === undefined) {
                            if (this.track.kind === 'audio') {
                                this._dtmf = this._pc.createDTMFSender(this.track);
                            } else {
                                this._dtmf = null;
                            }
                        }
                        return this._dtmf;
                    }
                });
            }
        }

        function shimGetStats(window) {
            if (!window.RTCPeerConnection) {
                return;
            }

            var origGetStats = window.RTCPeerConnection.prototype.getStats;
            window.RTCPeerConnection.prototype.getStats = function getStats() {
                var _this5 = this;

                var _arguments = Array.prototype.slice.call(arguments),
                    selector = _arguments[0],
                    onSucc = _arguments[1],
                    onErr = _arguments[2];

                // If selector is a function then we are in the old style stats so just
                // pass back the original getStats format to avoid breaking old users.


                if (arguments.length > 0 && typeof selector === 'function') {
                    return origGetStats.apply(this, arguments);
                }

                // When spec-style getStats is supported, return those when called with
                // either no arguments or the selector argument is null.
                if (origGetStats.length === 0 && (arguments.length === 0 || typeof selector !== 'function')) {
                    return origGetStats.apply(this, []);
                }

                var fixChromeStats_ = function fixChromeStats_(response) {
                    var standardReport = {};
                    var reports = response.result();
                    reports.forEach(function (report) {
                        var standardStats = {
                            id: report.id,
                            timestamp: report.timestamp,
                            type: {
                                localcandidate: 'local-candidate',
                                remotecandidate: 'remote-candidate'
                            }[report.type] || report.type
                        };
                        report.names().forEach(function (name) {
                            standardStats[name] = report.stat(name);
                        });
                        standardReport[standardStats.id] = standardStats;
                    });

                    return standardReport;
                };

                // shim getStats with maplike support
                var makeMapStats = function makeMapStats(stats) {
                    return new Map(Object.keys(stats).map(function (key) {
                        return [key, stats[key]];
                    }));
                };

                if (arguments.length >= 2) {
                    var successCallbackWrapper_ = function successCallbackWrapper_(response) {
                        onSucc(makeMapStats(fixChromeStats_(response)));
                    };

                    return origGetStats.apply(this, [successCallbackWrapper_, selector]);
                }

                // promise-support
                return new Promise(function (resolve, reject) {
                    origGetStats.apply(_this5, [function (response) {
                        resolve(makeMapStats(fixChromeStats_(response)));
                    }, reject]);
                }).then(onSucc, onErr);
            };
        }

        function shimSenderReceiverGetStats(window) {
            if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender && window.RTCRtpReceiver)) {
                return;
            }

            // shim sender stats.
            if (!('getStats' in window.RTCRtpSender.prototype)) {
                var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
                if (origGetSenders) {
                    window.RTCPeerConnection.prototype.getSenders = function getSenders() {
                        var _this6 = this;

                        var senders = origGetSenders.apply(this, []);
                        senders.forEach(function (sender) {
                            return sender._pc = _this6;
                        });
                        return senders;
                    };
                }

                var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
                if (origAddTrack) {
                    window.RTCPeerConnection.prototype.addTrack = function addTrack() {
                        var sender = origAddTrack.apply(this, arguments);
                        sender._pc = this;
                        return sender;
                    };
                }
                window.RTCRtpSender.prototype.getStats = function getStats() {
                    var sender = this;
                    return this._pc.getStats().then(function (result) {
                        return (
                            /* Note: this will include stats of all senders that
           *   send a track with the same id as sender.track as
           *   it is not possible to identify the RTCRtpSender.
           */
                            utils.filterStats(result, sender.track, true)
                        );
                    });
                };
            }

            // shim receiver stats.
            if (!('getStats' in window.RTCRtpReceiver.prototype)) {
                var origGetReceivers = window.RTCPeerConnection.prototype.getReceivers;
                if (origGetReceivers) {
                    window.RTCPeerConnection.prototype.getReceivers = function getReceivers() {
                        var _this7 = this;

                        var receivers = origGetReceivers.apply(this, []);
                        receivers.forEach(function (receiver) {
                            return receiver._pc = _this7;
                        });
                        return receivers;
                    };
                }
                utils.wrapPeerConnectionEvent(window, 'track', function (e) {
                    e.receiver._pc = e.srcElement;
                    return e;
                });
                window.RTCRtpReceiver.prototype.getStats = function getStats() {
                    var receiver = this;
                    return this._pc.getStats().then(function (result) {
                        return utils.filterStats(result, receiver.track, false);
                    });
                };
            }

            if (!('getStats' in window.RTCRtpSender.prototype && 'getStats' in window.RTCRtpReceiver.prototype)) {
                return;
            }

            // shim RTCPeerConnection.getStats(track).
            var origGetStats = window.RTCPeerConnection.prototype.getStats;
            window.RTCPeerConnection.prototype.getStats = function getStats() {
                if (arguments.length > 0 && arguments[0] instanceof window.MediaStreamTrack) {
                    var track = arguments[0];
                    var sender = void 0;
                    var receiver = void 0;
                    var err = void 0;
                    this.getSenders().forEach(function (s) {
                        if (s.track === track) {
                            if (sender) {
                                err = true;
                            } else {
                                sender = s;
                            }
                        }
                    });
                    this.getReceivers().forEach(function (r) {
                        if (r.track === track) {
                            if (receiver) {
                                err = true;
                            } else {
                                receiver = r;
                            }
                        }
                        return r.track === track;
                    });
                    if (err || sender && receiver) {
                        return Promise.reject(new DOMException('There are more than one sender or receiver for the track.', 'InvalidAccessError'));
                    } else if (sender) {
                        return sender.getStats();
                    } else if (receiver) {
                        return receiver.getStats();
                    }
                    return Promise.reject(new DOMException('There is no sender or receiver for the track.', 'InvalidAccessError'));
                }
                return origGetStats.apply(this, arguments);
            };
        }

        function shimAddTrackRemoveTrackWithNative(window) {
            // shim addTrack/removeTrack with native variants in order to make
            // the interactions with legacy getLocalStreams behave as in other browsers.
            // Keeps a mapping stream.id => [stream, rtpsenders...]
            window.RTCPeerConnection.prototype.getLocalStreams = function getLocalStreams() {
                var _this8 = this;

                this._shimmedLocalStreams = this._shimmedLocalStreams || {};
                return Object.keys(this._shimmedLocalStreams).map(function (streamId) {
                    return _this8._shimmedLocalStreams[streamId][0];
                });
            };

            var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
            window.RTCPeerConnection.prototype.addTrack = function addTrack(track, stream) {
                if (!stream) {
                    return origAddTrack.apply(this, arguments);
                }
                this._shimmedLocalStreams = this._shimmedLocalStreams || {};

                var sender = origAddTrack.apply(this, arguments);
                if (!this._shimmedLocalStreams[stream.id]) {
                    this._shimmedLocalStreams[stream.id] = [stream, sender];
                } else if (this._shimmedLocalStreams[stream.id].indexOf(sender) === -1) {
                    this._shimmedLocalStreams[stream.id].push(sender);
                }
                return sender;
            };

            var origAddStream = window.RTCPeerConnection.prototype.addStream;
            window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
                var _this9 = this;

                this._shimmedLocalStreams = this._shimmedLocalStreams || {};

                stream.getTracks().forEach(function (track) {
                    var alreadyExists = _this9.getSenders().find(function (s) {
                        return s.track === track;
                    });
                    if (alreadyExists) {
                        throw new DOMException('Track already exists.', 'InvalidAccessError');
                    }
                });
                var existingSenders = this.getSenders();
                origAddStream.apply(this, arguments);
                var newSenders = this.getSenders().filter(function (newSender) {
                    return existingSenders.indexOf(newSender) === -1;
                });
                this._shimmedLocalStreams[stream.id] = [stream].concat(newSenders);
            };

            var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
            window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
                this._shimmedLocalStreams = this._shimmedLocalStreams || {};
                delete this._shimmedLocalStreams[stream.id];
                return origRemoveStream.apply(this, arguments);
            };

            var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
            window.RTCPeerConnection.prototype.removeTrack = function removeTrack(sender) {
                var _this10 = this;

                this._shimmedLocalStreams = this._shimmedLocalStreams || {};
                if (sender) {
                    Object.keys(this._shimmedLocalStreams).forEach(function (streamId) {
                        var idx = _this10._shimmedLocalStreams[streamId].indexOf(sender);
                        if (idx !== -1) {
                            _this10._shimmedLocalStreams[streamId].splice(idx, 1);
                        }
                        if (_this10._shimmedLocalStreams[streamId].length === 1) {
                            delete _this10._shimmedLocalStreams[streamId];
                        }
                    });
                }
                return origRemoveTrack.apply(this, arguments);
            };
        }

        function shimAddTrackRemoveTrack(window) {
            if (!window.RTCPeerConnection) {
                return;
            }
            var browserDetails = utils.detectBrowser(window);
            // shim addTrack and removeTrack.
            if (window.RTCPeerConnection.prototype.addTrack && browserDetails.version >= 65) {
                return shimAddTrackRemoveTrackWithNative(window);
            }

            // also shim pc.getLocalStreams when addTrack is shimmed
            // to return the original streams.
            var origGetLocalStreams = window.RTCPeerConnection.prototype.getLocalStreams;
            window.RTCPeerConnection.prototype.getLocalStreams = function getLocalStreams() {
                var _this11 = this;

                var nativeStreams = origGetLocalStreams.apply(this);
                this._reverseStreams = this._reverseStreams || {};
                return nativeStreams.map(function (stream) {
                    return _this11._reverseStreams[stream.id];
                });
            };

            var origAddStream = window.RTCPeerConnection.prototype.addStream;
            window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
                var _this12 = this;

                this._streams = this._streams || {};
                this._reverseStreams = this._reverseStreams || {};

                stream.getTracks().forEach(function (track) {
                    var alreadyExists = _this12.getSenders().find(function (s) {
                        return s.track === track;
                    });
                    if (alreadyExists) {
                        throw new DOMException('Track already exists.', 'InvalidAccessError');
                    }
                });
                // Add identity mapping for consistency with addTrack.
                // Unless this is being used with a stream from addTrack.
                if (!this._reverseStreams[stream.id]) {
                    var newStream = new window.MediaStream(stream.getTracks());
                    this._streams[stream.id] = newStream;
                    this._reverseStreams[newStream.id] = stream;
                    stream = newStream;
                }
                origAddStream.apply(this, [stream]);
            };

            var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
            window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
                this._streams = this._streams || {};
                this._reverseStreams = this._reverseStreams || {};

                origRemoveStream.apply(this, [this._streams[stream.id] || stream]);
                delete this._reverseStreams[this._streams[stream.id] ? this._streams[stream.id].id : stream.id];
                delete this._streams[stream.id];
            };

            window.RTCPeerConnection.prototype.addTrack = function addTrack(track, stream) {
                var _this13 = this;

                if (this.signalingState === 'closed') {
                    throw new DOMException('The RTCPeerConnection\'s signalingState is \'closed\'.', 'InvalidStateError');
                }
                var streams = [].slice.call(arguments, 1);
                if (streams.length !== 1 || !streams[0].getTracks().find(function (t) {
                    return t === track;
                })) {
                    // this is not fully correct but all we can manage without
                    // [[associated MediaStreams]] internal slot.
                    throw new DOMException('The adapter.js addTrack polyfill only supports a single ' + ' stream which is associated with the specified track.', 'NotSupportedError');
                }

                var alreadyExists = this.getSenders().find(function (s) {
                    return s.track === track;
                });
                if (alreadyExists) {
                    throw new DOMException('Track already exists.', 'InvalidAccessError');
                }

                this._streams = this._streams || {};
                this._reverseStreams = this._reverseStreams || {};
                var oldStream = this._streams[stream.id];
                if (oldStream) {
                    // this is using odd Chrome behaviour, use with caution:
                    // https://bugs.chromium.org/p/webrtc/issues/detail?id=7815
                    // Note: we rely on the high-level addTrack/dtmf shim to
                    // create the sender with a dtmf sender.
                    oldStream.addTrack(track);

                    // Trigger ONN async.
                    Promise.resolve().then(function () {
                        _this13.dispatchEvent(new Event('negotiationneeded'));
                    });
                } else {
                    var newStream = new window.MediaStream([track]);
                    this._streams[stream.id] = newStream;
                    this._reverseStreams[newStream.id] = stream;
                    this.addStream(newStream);
                }
                return this.getSenders().find(function (s) {
                    return s.track === track;
                });
            };

            // replace the internal stream id with the external one and
            // vice versa.
            function replaceInternalStreamId(pc, description) {
                var sdp = description.sdp;
                Object.keys(pc._reverseStreams || []).forEach(function (internalId) {
                    var externalStream = pc._reverseStreams[internalId];
                    var internalStream = pc._streams[externalStream.id];
                    sdp = sdp.replace(new RegExp(internalStream.id, 'g'), externalStream.id);
                });
                return new RTCSessionDescription({
                    type: description.type,
                    sdp: sdp
                });
            }
            function replaceExternalStreamId(pc, description) {
                var sdp = description.sdp;
                Object.keys(pc._reverseStreams || []).forEach(function (internalId) {
                    var externalStream = pc._reverseStreams[internalId];
                    var internalStream = pc._streams[externalStream.id];
                    sdp = sdp.replace(new RegExp(externalStream.id, 'g'), internalStream.id);
                });
                return new RTCSessionDescription({
                    type: description.type,
                    sdp: sdp
                });
            }
            ['createOffer', 'createAnswer'].forEach(function (method) {
                var nativeMethod = window.RTCPeerConnection.prototype[method];
                var methodObj = _defineProperty({}, method, function () {
                    var _this14 = this;

                    var args = arguments;
                    var isLegacyCall = arguments.length && typeof arguments[0] === 'function';
                    if (isLegacyCall) {
                        return nativeMethod.apply(this, [function (description) {
                            var desc = replaceInternalStreamId(_this14, description);
                            args[0].apply(null, [desc]);
                        }, function (err) {
                            if (args[1]) {
                                args[1].apply(null, err);
                            }
                        }, arguments[2]]);
                    }
                    return nativeMethod.apply(this, arguments).then(function (description) {
                        return replaceInternalStreamId(_this14, description);
                    });
                });
                window.RTCPeerConnection.prototype[method] = methodObj[method];
            });

            var origSetLocalDescription = window.RTCPeerConnection.prototype.setLocalDescription;
            window.RTCPeerConnection.prototype.setLocalDescription = function setLocalDescription() {
                if (!arguments.length || !arguments[0].type) {
                    return origSetLocalDescription.apply(this, arguments);
                }
                arguments[0] = replaceExternalStreamId(this, arguments[0]);
                return origSetLocalDescription.apply(this, arguments);
            };

            // TODO: mangle getStats: https://w3c.github.io/webrtc-stats/#dom-rtcmediastreamstats-streamidentifier

            var origLocalDescription = Object.getOwnPropertyDescriptor(window.RTCPeerConnection.prototype, 'localDescription');
            Object.defineProperty(window.RTCPeerConnection.prototype, 'localDescription', {
                get: function get() {
                    var description = origLocalDescription.get.apply(this);
                    if (description.type === '') {
                        return description;
                    }
                    return replaceInternalStreamId(this, description);
                }
            });

            window.RTCPeerConnection.prototype.removeTrack = function removeTrack(sender) {
                var _this15 = this;

                if (this.signalingState === 'closed') {
                    throw new DOMException('The RTCPeerConnection\'s signalingState is \'closed\'.', 'InvalidStateError');
                }
                // We can not yet check for sender instanceof RTCRtpSender
                // since we shim RTPSender. So we check if sender._pc is set.
                if (!sender._pc) {
                    throw new DOMException('Argument 1 of RTCPeerConnection.removeTrack ' + 'does not implement interface RTCRtpSender.', 'TypeError');
                }
                var isLocal = sender._pc === this;
                if (!isLocal) {
                    throw new DOMException('Sender was not created by this connection.', 'InvalidAccessError');
                }

                // Search for the native stream the senders track belongs to.
                this._streams = this._streams || {};
                var stream = void 0;
                Object.keys(this._streams).forEach(function (streamid) {
                    var hasTrack = _this15._streams[streamid].getTracks().find(function (track) {
                        return sender.track === track;
                    });
                    if (hasTrack) {
                        stream = _this15._streams[streamid];
                    }
                });

                if (stream) {
                    if (stream.getTracks().length === 1) {
                        // if this is the last track of the stream, remove the stream. This
                        // takes care of any shimmed _senders.
                        this.removeStream(this._reverseStreams[stream.id]);
                    } else {
                        // relying on the same odd chrome behaviour as above.
                        stream.removeTrack(sender.track);
                    }
                    this.dispatchEvent(new Event('negotiationneeded'));
                }
            };
        }

        function shimPeerConnection(window) {
            var browserDetails = utils.detectBrowser(window);

            if (!window.RTCPeerConnection && window.webkitRTCPeerConnection) {
                // very basic support for old versions.
                window.RTCPeerConnection = window.webkitRTCPeerConnection;
            }
            if (!window.RTCPeerConnection) {
                return;
            }

            var addIceCandidateNullSupported = window.RTCPeerConnection.prototype.addIceCandidate.length === 0;

            // shim implicit creation of RTCSessionDescription/RTCIceCandidate
            if (browserDetails.version < 53) {
                ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'].forEach(function (method) {
                    var nativeMethod = window.RTCPeerConnection.prototype[method];
                    var methodObj = _defineProperty({}, method, function () {
                        arguments[0] = new (method === 'addIceCandidate' ? window.RTCIceCandidate : window.RTCSessionDescription)(arguments[0]);
                        return nativeMethod.apply(this, arguments);
                    });
                    window.RTCPeerConnection.prototype[method] = methodObj[method];
                });
            }

            // support for addIceCandidate(null or undefined)
            var nativeAddIceCandidate = window.RTCPeerConnection.prototype.addIceCandidate;
            window.RTCPeerConnection.prototype.addIceCandidate = function addIceCandidate() {
                if (!addIceCandidateNullSupported && !arguments[0]) {
                    if (arguments[1]) {
                        arguments[1].apply(null);
                    }
                    return Promise.resolve();
                }
                // Firefox 68+ emits and processes {candidate: "", ...}, ignore
                // in older versions. Native support planned for Chrome M77.
                if (browserDetails.version < 78 && arguments[0] && arguments[0].candidate === '') {
                    return Promise.resolve();
                }
                return nativeAddIceCandidate.apply(this, arguments);
            };
        }

// Attempt to fix ONN in plan-b mode.
        function fixNegotiationNeeded(window) {
            var browserDetails = utils.detectBrowser(window);
            utils.wrapPeerConnectionEvent(window, 'negotiationneeded', function (e) {
                var pc = e.target;
                if (browserDetails.version < 72 || pc.getConfiguration && pc.getConfiguration().sdpSemantics === 'plan-b') {
                    if (pc.signalingState !== 'stable') {
                        return;
                    }
                }
                return e;
            });
        }

    },{"../utils.js":15,"./getdisplaymedia":4,"./getusermedia":5}],4:[function(require,module,exports){
        /*
 *  Copyright (c) 2018 The adapter.js project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });
        exports.shimGetDisplayMedia = shimGetDisplayMedia;
        function shimGetDisplayMedia(window, getSourceId) {
            if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
                return;
            }
            if (!window.navigator.mediaDevices) {
                return;
            }
            // getSourceId is a function that returns a promise resolving with
            // the sourceId of the screen/window/tab to be shared.
            if (typeof getSourceId !== 'function') {
                console.error('shimGetDisplayMedia: getSourceId argument is not ' + 'a function');
                return;
            }
            window.navigator.mediaDevices.getDisplayMedia = function getDisplayMedia(constraints) {
                return getSourceId(constraints).then(function (sourceId) {
                    var widthSpecified = constraints.video && constraints.video.width;
                    var heightSpecified = constraints.video && constraints.video.height;
                    var frameRateSpecified = constraints.video && constraints.video.frameRate;
                    constraints.video = {
                        mandatory: {
                            chromeMediaSource: 'desktop',
                            chromeMediaSourceId: sourceId,
                            maxFrameRate: frameRateSpecified || 3
                        }
                    };
                    if (widthSpecified) {
                        constraints.video.mandatory.maxWidth = widthSpecified;
                    }
                    if (heightSpecified) {
                        constraints.video.mandatory.maxHeight = heightSpecified;
                    }
                    return window.navigator.mediaDevices.getUserMedia(constraints);
                });
            };
        }

    },{}],5:[function(require,module,exports){
        /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });

        var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

        exports.shimGetUserMedia = shimGetUserMedia;

        var _utils = require('../utils.js');

        var utils = _interopRequireWildcard(_utils);

        function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

        var logging = utils.log;

        function shimGetUserMedia(window) {
            var navigator = window && window.navigator;

            if (!navigator.mediaDevices) {
                return;
            }

            var browserDetails = utils.detectBrowser(window);

            var constraintsToChrome_ = function constraintsToChrome_(c) {
                if ((typeof c === 'undefined' ? 'undefined' : _typeof(c)) !== 'object' || c.mandatory || c.optional) {
                    return c;
                }
                var cc = {};
                Object.keys(c).forEach(function (key) {
                    if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
                        return;
                    }
                    var r = _typeof(c[key]) === 'object' ? c[key] : { ideal: c[key] };
                    if (r.exact !== undefined && typeof r.exact === 'number') {
                        r.min = r.max = r.exact;
                    }
                    var oldname_ = function oldname_(prefix, name) {
                        if (prefix) {
                            return prefix + name.charAt(0).toUpperCase() + name.slice(1);
                        }
                        return name === 'deviceId' ? 'sourceId' : name;
                    };
                    if (r.ideal !== undefined) {
                        cc.optional = cc.optional || [];
                        var oc = {};
                        if (typeof r.ideal === 'number') {
                            oc[oldname_('min', key)] = r.ideal;
                            cc.optional.push(oc);
                            oc = {};
                            oc[oldname_('max', key)] = r.ideal;
                            cc.optional.push(oc);
                        } else {
                            oc[oldname_('', key)] = r.ideal;
                            cc.optional.push(oc);
                        }
                    }
                    if (r.exact !== undefined && typeof r.exact !== 'number') {
                        cc.mandatory = cc.mandatory || {};
                        cc.mandatory[oldname_('', key)] = r.exact;
                    } else {
                        ['min', 'max'].forEach(function (mix) {
                            if (r[mix] !== undefined) {
                                cc.mandatory = cc.mandatory || {};
                                cc.mandatory[oldname_(mix, key)] = r[mix];
                            }
                        });
                    }
                });
                if (c.advanced) {
                    cc.optional = (cc.optional || []).concat(c.advanced);
                }
                return cc;
            };

            var shimConstraints_ = function shimConstraints_(constraints, func) {
                if (browserDetails.version >= 61) {
                    return func(constraints);
                }
                constraints = JSON.parse(JSON.stringify(constraints));
                if (constraints && _typeof(constraints.audio) === 'object') {
                    var remap = function remap(obj, a, b) {
                        if (a in obj && !(b in obj)) {
                            obj[b] = obj[a];
                            delete obj[a];
                        }
                    };
                    constraints = JSON.parse(JSON.stringify(constraints));
                    remap(constraints.audio, 'autoGainControl', 'googAutoGainControl');
                    remap(constraints.audio, 'noiseSuppression', 'googNoiseSuppression');
                    constraints.audio = constraintsToChrome_(constraints.audio);
                }
                if (constraints && _typeof(constraints.video) === 'object') {
                    // Shim facingMode for mobile & surface pro.
                    var face = constraints.video.facingMode;
                    face = face && ((typeof face === 'undefined' ? 'undefined' : _typeof(face)) === 'object' ? face : { ideal: face });
                    var getSupportedFacingModeLies = browserDetails.version < 66;

                    if (face && (face.exact === 'user' || face.exact === 'environment' || face.ideal === 'user' || face.ideal === 'environment') && !(navigator.mediaDevices.getSupportedConstraints && navigator.mediaDevices.getSupportedConstraints().facingMode && !getSupportedFacingModeLies)) {
                        delete constraints.video.facingMode;
                        var matches = void 0;
                        if (face.exact === 'environment' || face.ideal === 'environment') {
                            matches = ['back', 'rear'];
                        } else if (face.exact === 'user' || face.ideal === 'user') {
                            matches = ['front'];
                        }
                        if (matches) {
                            // Look for matches in label, or use last cam for back (typical).
                            return navigator.mediaDevices.enumerateDevices().then(function (devices) {
                                devices = devices.filter(function (d) {
                                    return d.kind === 'videoinput';
                                });
                                var dev = devices.find(function (d) {
                                    return matches.some(function (match) {
                                        return d.label.toLowerCase().includes(match);
                                    });
                                });
                                if (!dev && devices.length && matches.includes('back')) {
                                    dev = devices[devices.length - 1]; // more likely the back cam
                                }
                                if (dev) {
                                    constraints.video.deviceId = face.exact ? { exact: dev.deviceId } : { ideal: dev.deviceId };
                                }
                                constraints.video = constraintsToChrome_(constraints.video);
                                logging('chrome: ' + JSON.stringify(constraints));
                                return func(constraints);
                            });
                        }
                    }
                    constraints.video = constraintsToChrome_(constraints.video);
                }
                logging('chrome: ' + JSON.stringify(constraints));
                return func(constraints);
            };

            var shimError_ = function shimError_(e) {
                if (browserDetails.version >= 64) {
                    return e;
                }
                return {
                    name: {
                        PermissionDeniedError: 'NotAllowedError',
                        PermissionDismissedError: 'NotAllowedError',
                        InvalidStateError: 'NotAllowedError',
                        DevicesNotFoundError: 'NotFoundError',
                        ConstraintNotSatisfiedError: 'OverconstrainedError',
                        TrackStartError: 'NotReadableError',
                        MediaDeviceFailedDueToShutdown: 'NotAllowedError',
                        MediaDeviceKillSwitchOn: 'NotAllowedError',
                        TabCaptureError: 'AbortError',
                        ScreenCaptureError: 'AbortError',
                        DeviceCaptureError: 'AbortError'
                    }[e.name] || e.name,
                    message: e.message,
                    constraint: e.constraint || e.constraintName,
                    toString: function toString() {
                        return this.name + (this.message && ': ') + this.message;
                    }
                };
            };

            var getUserMedia_ = function getUserMedia_(constraints, onSuccess, onError) {
                shimConstraints_(constraints, function (c) {
                    navigator.webkitGetUserMedia(c, onSuccess, function (e) {
                        if (onError) {
                            onError(shimError_(e));
                        }
                    });
                });
            };
            navigator.getUserMedia = getUserMedia_.bind(navigator);

            // Even though Chrome 45 has navigator.mediaDevices and a getUserMedia
            // function which returns a Promise, it does not accept spec-style
            // constraints.
            if (navigator.mediaDevices.getUserMedia) {
                var origGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices);
                navigator.mediaDevices.getUserMedia = function (cs) {
                    return shimConstraints_(cs, function (c) {
                        return origGetUserMedia(c).then(function (stream) {
                            if (c.audio && !stream.getAudioTracks().length || c.video && !stream.getVideoTracks().length) {
                                stream.getTracks().forEach(function (track) {
                                    track.stop();
                                });
                                throw new DOMException('', 'NotFoundError');
                            }
                            return stream;
                        }, function (e) {
                            return Promise.reject(shimError_(e));
                        });
                    });
                };
            }
        }

    },{"../utils.js":15}],6:[function(require,module,exports){
        /*
 *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });

        var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

        exports.shimRTCIceCandidate = shimRTCIceCandidate;
        exports.shimMaxMessageSize = shimMaxMessageSize;
        exports.shimSendThrowTypeError = shimSendThrowTypeError;
        exports.shimConnectionState = shimConnectionState;
        exports.removeAllowExtmapMixed = removeAllowExtmapMixed;

        var _sdp = require('sdp');

        var _sdp2 = _interopRequireDefault(_sdp);

        var _utils = require('./utils');

        var utils = _interopRequireWildcard(_utils);

        function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

        function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

        function shimRTCIceCandidate(window) {
            // foundation is arbitrarily chosen as an indicator for full support for
            // https://w3c.github.io/webrtc-pc/#rtcicecandidate-interface
            if (!window.RTCIceCandidate || window.RTCIceCandidate && 'foundation' in window.RTCIceCandidate.prototype) {
                return;
            }

            var NativeRTCIceCandidate = window.RTCIceCandidate;
            window.RTCIceCandidate = function RTCIceCandidate(args) {
                // Remove the a= which shouldn't be part of the candidate string.
                if ((typeof args === 'undefined' ? 'undefined' : _typeof(args)) === 'object' && args.candidate && args.candidate.indexOf('a=') === 0) {
                    args = JSON.parse(JSON.stringify(args));
                    args.candidate = args.candidate.substr(2);
                }

                if (args.candidate && args.candidate.length) {
                    // Augment the native candidate with the parsed fields.
                    var nativeCandidate = new NativeRTCIceCandidate(args);
                    var parsedCandidate = _sdp2.default.parseCandidate(args.candidate);
                    var augmentedCandidate = Object.assign(nativeCandidate, parsedCandidate);

                    // Add a serializer that does not serialize the extra attributes.
                    augmentedCandidate.toJSON = function toJSON() {
                        return {
                            candidate: augmentedCandidate.candidate,
                            sdpMid: augmentedCandidate.sdpMid,
                            sdpMLineIndex: augmentedCandidate.sdpMLineIndex,
                            usernameFragment: augmentedCandidate.usernameFragment
                        };
                    };
                    return augmentedCandidate;
                }
                return new NativeRTCIceCandidate(args);
            };
            window.RTCIceCandidate.prototype = NativeRTCIceCandidate.prototype;

            // Hook up the augmented candidate in onicecandidate and
            // addEventListener('icecandidate', ...)
            utils.wrapPeerConnectionEvent(window, 'icecandidate', function (e) {
                if (e.candidate) {
                    Object.defineProperty(e, 'candidate', {
                        value: new window.RTCIceCandidate(e.candidate),
                        writable: 'false'
                    });
                }
                return e;
            });
        }

        function shimMaxMessageSize(window) {
            if (!window.RTCPeerConnection) {
                return;
            }
            var browserDetails = utils.detectBrowser(window);

            if (!('sctp' in window.RTCPeerConnection.prototype)) {
                Object.defineProperty(window.RTCPeerConnection.prototype, 'sctp', {
                    get: function get() {
                        return typeof this._sctp === 'undefined' ? null : this._sctp;
                    }
                });
            }

            var sctpInDescription = function sctpInDescription(description) {
                if (!description || !description.sdp) {
                    return false;
                }
                var sections = _sdp2.default.splitSections(description.sdp);
                sections.shift();
                return sections.some(function (mediaSection) {
                    var mLine = _sdp2.default.parseMLine(mediaSection);
                    return mLine && mLine.kind === 'application' && mLine.protocol.indexOf('SCTP') !== -1;
                });
            };

            var getRemoteFirefoxVersion = function getRemoteFirefoxVersion(description) {
                // TODO: Is there a better solution for detecting Firefox?
                var match = description.sdp.match(/mozilla...THIS_IS_SDPARTA-(\d+)/);
                if (match === null || match.length < 2) {
                    return -1;
                }
                var version = parseInt(match[1], 10);
                // Test for NaN (yes, this is ugly)
                return version !== version ? -1 : version;
            };

            var getCanSendMaxMessageSize = function getCanSendMaxMessageSize(remoteIsFirefox) {
                // Every implementation we know can send at least 64 KiB.
                // Note: Although Chrome is technically able to send up to 256 KiB, the
                //       data does not reach the other peer reliably.
                //       See: https://bugs.chromium.org/p/webrtc/issues/detail?id=8419
                var canSendMaxMessageSize = 65536;
                if (browserDetails.browser === 'firefox') {
                    if (browserDetails.version < 57) {
                        if (remoteIsFirefox === -1) {
                            // FF < 57 will send in 16 KiB chunks using the deprecated PPID
                            // fragmentation.
                            canSendMaxMessageSize = 16384;
                        } else {
                            // However, other FF (and RAWRTC) can reassemble PPID-fragmented
                            // messages. Thus, supporting ~2 GiB when sending.
                            canSendMaxMessageSize = 2147483637;
                        }
                    } else if (browserDetails.version < 60) {
                        // Currently, all FF >= 57 will reset the remote maximum message size
                        // to the default value when a data channel is created at a later
                        // stage. :(
                        // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831
                        canSendMaxMessageSize = browserDetails.version === 57 ? 65535 : 65536;
                    } else {
                        // FF >= 60 supports sending ~2 GiB
                        canSendMaxMessageSize = 2147483637;
                    }
                }
                return canSendMaxMessageSize;
            };

            var getMaxMessageSize = function getMaxMessageSize(description, remoteIsFirefox) {
                // Note: 65536 bytes is the default value from the SDP spec. Also,
                //       every implementation we know supports receiving 65536 bytes.
                var maxMessageSize = 65536;

                // FF 57 has a slightly incorrect default remote max message size, so
                // we need to adjust it here to avoid a failure when sending.
                // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1425697
                if (browserDetails.browser === 'firefox' && browserDetails.version === 57) {
                    maxMessageSize = 65535;
                }

                var match = _sdp2.default.matchPrefix(description.sdp, 'a=max-message-size:');
                if (match.length > 0) {
                    maxMessageSize = parseInt(match[0].substr(19), 10);
                } else if (browserDetails.browser === 'firefox' && remoteIsFirefox !== -1) {
                    // If the maximum message size is not present in the remote SDP and
                    // both local and remote are Firefox, the remote peer can receive
                    // ~2 GiB.
                    maxMessageSize = 2147483637;
                }
                return maxMessageSize;
            };

            var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription;
            window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription() {
                this._sctp = null;
                // Chrome decided to not expose .sctp in plan-b mode.
                // As usual, adapter.js has to do an 'ugly worakaround'
                // to cover up the mess.
                if (browserDetails.browser === 'chrome' && browserDetails.version >= 76) {
                    var _getConfiguration = this.getConfiguration(),
                        sdpSemantics = _getConfiguration.sdpSemantics;

                    if (sdpSemantics === 'plan-b') {
                        Object.defineProperty(this, 'sctp', {
                            get: function get() {
                                return typeof this._sctp === 'undefined' ? null : this._sctp;
                            },

                            enumerable: true,
                            configurable: true
                        });
                    }
                }

                if (sctpInDescription(arguments[0])) {
                    // Check if the remote is FF.
                    var isFirefox = getRemoteFirefoxVersion(arguments[0]);

                    // Get the maximum message size the local peer is capable of sending
                    var canSendMMS = getCanSendMaxMessageSize(isFirefox);

                    // Get the maximum message size of the remote peer.
                    var remoteMMS = getMaxMessageSize(arguments[0], isFirefox);

                    // Determine final maximum message size
                    var maxMessageSize = void 0;
                    if (canSendMMS === 0 && remoteMMS === 0) {
                        maxMessageSize = Number.POSITIVE_INFINITY;
                    } else if (canSendMMS === 0 || remoteMMS === 0) {
                        maxMessageSize = Math.max(canSendMMS, remoteMMS);
                    } else {
                        maxMessageSize = Math.min(canSendMMS, remoteMMS);
                    }

                    // Create a dummy RTCSctpTransport object and the 'maxMessageSize'
                    // attribute.
                    var sctp = {};
                    Object.defineProperty(sctp, 'maxMessageSize', {
                        get: function get() {
                            return maxMessageSize;
                        }
                    });
                    this._sctp = sctp;
                }

                return origSetRemoteDescription.apply(this, arguments);
            };
        }

        function shimSendThrowTypeError(window) {
            if (!(window.RTCPeerConnection && 'createDataChannel' in window.RTCPeerConnection.prototype)) {
                return;
            }

            // Note: Although Firefox >= 57 has a native implementation, the maximum
            //       message size can be reset for all data channels at a later stage.
            //       See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831

            function wrapDcSend(dc, pc) {
                var origDataChannelSend = dc.send;
                dc.send = function send() {
                    var data = arguments[0];
                    var length = data.length || data.size || data.byteLength;
                    if (dc.readyState === 'open' && pc.sctp && length > pc.sctp.maxMessageSize) {
                        throw new TypeError('Message too large (can send a maximum of ' + pc.sctp.maxMessageSize + ' bytes)');
                    }
                    return origDataChannelSend.apply(dc, arguments);
                };
            }
            var origCreateDataChannel = window.RTCPeerConnection.prototype.createDataChannel;
            window.RTCPeerConnection.prototype.createDataChannel = function createDataChannel() {
                var dataChannel = origCreateDataChannel.apply(this, arguments);
                wrapDcSend(dataChannel, this);
                return dataChannel;
            };
            utils.wrapPeerConnectionEvent(window, 'datachannel', function (e) {
                wrapDcSend(e.channel, e.target);
                return e;
            });
        }

        /* shims RTCConnectionState by pretending it is the same as iceConnectionState.
 * See https://bugs.chromium.org/p/webrtc/issues/detail?id=6145#c12
 * for why this is a valid hack in Chrome. In Firefox it is slightly incorrect
 * since DTLS failures would be hidden. See
 * https://bugzilla.mozilla.org/show_bug.cgi?id=1265827
 * for the Firefox tracking bug.
 */
        function shimConnectionState(window) {
            if (!window.RTCPeerConnection || 'connectionState' in window.RTCPeerConnection.prototype) {
                return;
            }
            var proto = window.RTCPeerConnection.prototype;
            Object.defineProperty(proto, 'connectionState', {
                get: function get() {
                    return {
                        completed: 'connected',
                        checking: 'connecting'
                    }[this.iceConnectionState] || this.iceConnectionState;
                },

                enumerable: true,
                configurable: true
            });
            Object.defineProperty(proto, 'onconnectionstatechange', {
                get: function get() {
                    return this._onconnectionstatechange || null;
                },
                set: function set(cb) {
                    if (this._onconnectionstatechange) {
                        this.removeEventListener('connectionstatechange', this._onconnectionstatechange);
                        delete this._onconnectionstatechange;
                    }
                    if (cb) {
                        this.addEventListener('connectionstatechange', this._onconnectionstatechange = cb);
                    }
                },

                enumerable: true,
                configurable: true
            });

            ['setLocalDescription', 'setRemoteDescription'].forEach(function (method) {
                var origMethod = proto[method];
                proto[method] = function () {
                    if (!this._connectionstatechangepoly) {
                        this._connectionstatechangepoly = function (e) {
                            var pc = e.target;
                            if (pc._lastConnectionState !== pc.connectionState) {
                                pc._lastConnectionState = pc.connectionState;
                                var newEvent = new Event('connectionstatechange', e);
                                pc.dispatchEvent(newEvent);
                            }
                            return e;
                        };
                        this.addEventListener('iceconnectionstatechange', this._connectionstatechangepoly);
                    }
                    return origMethod.apply(this, arguments);
                };
            });
        }

        function removeAllowExtmapMixed(window) {
            /* remove a=extmap-allow-mixed for webrtc.org < M71 */
            if (!window.RTCPeerConnection) {
                return;
            }
            var browserDetails = utils.detectBrowser(window);
            if (browserDetails.browser === 'chrome' && browserDetails.version >= 71) {
                return;
            }
            if (browserDetails.browser === 'safari' && browserDetails.version >= 605) {
                return;
            }
            var nativeSRD = window.RTCPeerConnection.prototype.setRemoteDescription;
            window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription(desc) {
                if (desc && desc.sdp && desc.sdp.indexOf('\na=extmap-allow-mixed') !== -1) {
                    desc.sdp = desc.sdp.split('\n').filter(function (line) {
                        return line.trim() !== 'a=extmap-allow-mixed';
                    }).join('\n');
                }
                return nativeSRD.apply(this, arguments);
            };
        }

    },{"./utils":15,"sdp":17}],7:[function(require,module,exports){
        /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });
        exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined;

        var _getusermedia = require('./getusermedia');

        Object.defineProperty(exports, 'shimGetUserMedia', {
            enumerable: true,
            get: function get() {
                return _getusermedia.shimGetUserMedia;
            }
        });

        var _getdisplaymedia = require('./getdisplaymedia');

        Object.defineProperty(exports, 'shimGetDisplayMedia', {
            enumerable: true,
            get: function get() {
                return _getdisplaymedia.shimGetDisplayMedia;
            }
        });
        exports.shimPeerConnection = shimPeerConnection;
        exports.shimReplaceTrack = shimReplaceTrack;

        var _utils = require('../utils');

        var utils = _interopRequireWildcard(_utils);

        var _filtericeservers = require('./filtericeservers');

        var _rtcpeerconnectionShim = require('rtcpeerconnection-shim');

        var _rtcpeerconnectionShim2 = _interopRequireDefault(_rtcpeerconnectionShim);

        function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

        function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

        function shimPeerConnection(window) {
            var browserDetails = utils.detectBrowser(window);

            if (window.RTCIceGatherer) {
                if (!window.RTCIceCandidate) {
                    window.RTCIceCandidate = function RTCIceCandidate(args) {
                        return args;
                    };
                }
                if (!window.RTCSessionDescription) {
                    window.RTCSessionDescription = function RTCSessionDescription(args) {
                        return args;
                    };
                }
                // this adds an additional event listener to MediaStrackTrack that signals
                // when a tracks enabled property was changed. Workaround for a bug in
                // addStream, see below. No longer required in 15025+
                if (browserDetails.version < 15025) {
                    var origMSTEnabled = Object.getOwnPropertyDescriptor(window.MediaStreamTrack.prototype, 'enabled');
                    Object.defineProperty(window.MediaStreamTrack.prototype, 'enabled', {
                        set: function set(value) {
                            origMSTEnabled.set.call(this, value);
                            var ev = new Event('enabled');
                            ev.enabled = value;
                            this.dispatchEvent(ev);
                        }
                    });
                }
            }

            // ORTC defines the DTMF sender a bit different.
            // https://github.com/w3c/ortc/issues/714
            if (window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
                Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
                    get: function get() {
                        if (this._dtmf === undefined) {
                            if (this.track.kind === 'audio') {
                                this._dtmf = new window.RTCDtmfSender(this);
                            } else if (this.track.kind === 'video') {
                                this._dtmf = null;
                            }
                        }
                        return this._dtmf;
                    }
                });
            }
            // Edge currently only implements the RTCDtmfSender, not the
            // RTCDTMFSender alias. See http://draft.ortc.org/#rtcdtmfsender2*
            if (window.RTCDtmfSender && !window.RTCDTMFSender) {
                window.RTCDTMFSender = window.RTCDtmfSender;
            }

            var RTCPeerConnectionShim = (0, _rtcpeerconnectionShim2.default)(window, browserDetails.version);
            window.RTCPeerConnection = function RTCPeerConnection(config) {
                if (config && config.iceServers) {
                    config.iceServers = (0, _filtericeservers.filterIceServers)(config.iceServers, browserDetails.version);
                    utils.log('ICE servers after filtering:', config.iceServers);
                }
                return new RTCPeerConnectionShim(config);
            };
            window.RTCPeerConnection.prototype = RTCPeerConnectionShim.prototype;
        }

        function shimReplaceTrack(window) {
            // ORTC has replaceTrack -- https://github.com/w3c/ortc/issues/614
            if (window.RTCRtpSender && !('replaceTrack' in window.RTCRtpSender.prototype)) {
                window.RTCRtpSender.prototype.replaceTrack = window.RTCRtpSender.prototype.setTrack;
            }
        }

    },{"../utils":15,"./filtericeservers":8,"./getdisplaymedia":9,"./getusermedia":10,"rtcpeerconnection-shim":16}],8:[function(require,module,exports){
        /*
 *  Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });
        exports.filterIceServers = filterIceServers;

        var _utils = require('../utils');

        var utils = _interopRequireWildcard(_utils);

        function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

// Edge does not like
// 1) stun: filtered after 14393 unless ?transport=udp is present
// 2) turn: that does not have all of turn:host:port?transport=udp
// 3) turn: with ipv6 addresses
// 4) turn: occurring muliple times
        function filterIceServers(iceServers, edgeVersion) {
            var hasTurn = false;
            iceServers = JSON.parse(JSON.stringify(iceServers));
            return iceServers.filter(function (server) {
                if (server && (server.urls || server.url)) {
                    var urls = server.urls || server.url;
                    if (server.url && !server.urls) {
                        utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
                    }
                    var isString = typeof urls === 'string';
                    if (isString) {
                        urls = [urls];
                    }
                    urls = urls.filter(function (url) {
                        // filter STUN unconditionally.
                        if (url.indexOf('stun:') === 0) {
                            return false;
                        }

                        var validTurn = url.startsWith('turn') && !url.startsWith('turn:[') && url.includes('transport=udp');
                        if (validTurn && !hasTurn) {
                            hasTurn = true;
                            return true;
                        }
                        return validTurn && !hasTurn;
                    });

                    delete server.url;
                    server.urls = isString ? urls[0] : urls;
                    return !!urls.length;
                }
            });
        }

    },{"../utils":15}],9:[function(require,module,exports){
        /*
 *  Copyright (c) 2018 The adapter.js project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });
        exports.shimGetDisplayMedia = shimGetDisplayMedia;
        function shimGetDisplayMedia(window) {
            if (!('getDisplayMedia' in window.navigator)) {
                return;
            }
            if (!window.navigator.mediaDevices) {
                return;
            }
            if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
                return;
            }
            window.navigator.mediaDevices.getDisplayMedia = window.navigator.getDisplayMedia.bind(window.navigator);
        }

    },{}],10:[function(require,module,exports){
        /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });
        exports.shimGetUserMedia = shimGetUserMedia;
        function shimGetUserMedia(window) {
            var navigator = window && window.navigator;

            var shimError_ = function shimError_(e) {
                return {
                    name: { PermissionDeniedError: 'NotAllowedError' }[e.name] || e.name,
                    message: e.message,
                    constraint: e.constraint,
                    toString: function toString() {
                        return this.name;
                    }
                };
            };

            // getUserMedia error shim.
            var origGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices);
            navigator.mediaDevices.getUserMedia = function (c) {
                return origGetUserMedia(c).catch(function (e) {
                    return Promise.reject(shimError_(e));
                });
            };
        }

    },{}],11:[function(require,module,exports){
        /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });
        exports.shimGetDisplayMedia = exports.shimGetUserMedia = undefined;

        var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

        var _getusermedia = require('./getusermedia');

        Object.defineProperty(exports, 'shimGetUserMedia', {
            enumerable: true,
            get: function get() {
                return _getusermedia.shimGetUserMedia;
            }
        });

        var _getdisplaymedia = require('./getdisplaymedia');

        Object.defineProperty(exports, 'shimGetDisplayMedia', {
            enumerable: true,
            get: function get() {
                return _getdisplaymedia.shimGetDisplayMedia;
            }
        });
        exports.shimOnTrack = shimOnTrack;
        exports.shimPeerConnection = shimPeerConnection;
        exports.shimSenderGetStats = shimSenderGetStats;
        exports.shimReceiverGetStats = shimReceiverGetStats;
        exports.shimRemoveStream = shimRemoveStream;
        exports.shimRTCDataChannel = shimRTCDataChannel;
        exports.shimAddTransceiver = shimAddTransceiver;
        exports.shimGetParameters = shimGetParameters;
        exports.shimCreateOffer = shimCreateOffer;
        exports.shimCreateAnswer = shimCreateAnswer;

        var _utils = require('../utils');

        var utils = _interopRequireWildcard(_utils);

        function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

        function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }

        function shimOnTrack(window) {
            if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCTrackEvent && 'receiver' in window.RTCTrackEvent.prototype && !('transceiver' in window.RTCTrackEvent.prototype)) {
                Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
                    get: function get() {
                        return { receiver: this.receiver };
                    }
                });
            }
        }

        function shimPeerConnection(window) {
            var browserDetails = utils.detectBrowser(window);

            if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !(window.RTCPeerConnection || window.mozRTCPeerConnection)) {
                return; // probably media.peerconnection.enabled=false in about:config
            }
            if (!window.RTCPeerConnection && window.mozRTCPeerConnection) {
                // very basic support for old versions.
                window.RTCPeerConnection = window.mozRTCPeerConnection;
            }

            if (browserDetails.version < 53) {
                // shim away need for obsolete RTCIceCandidate/RTCSessionDescription.
                ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'].forEach(function (method) {
                    var nativeMethod = window.RTCPeerConnection.prototype[method];
                    var methodObj = _defineProperty({}, method, function () {
                        arguments[0] = new (method === 'addIceCandidate' ? window.RTCIceCandidate : window.RTCSessionDescription)(arguments[0]);
                        return nativeMethod.apply(this, arguments);
                    });
                    window.RTCPeerConnection.prototype[method] = methodObj[method];
                });
            }

            // support for addIceCandidate(null or undefined)
            // as well as ignoring {sdpMid, candidate: ""}
            if (browserDetails.version < 68) {
                var nativeAddIceCandidate = window.RTCPeerConnection.prototype.addIceCandidate;
                window.RTCPeerConnection.prototype.addIceCandidate = function addIceCandidate() {
                    if (!arguments[0]) {
                        if (arguments[1]) {
                            arguments[1].apply(null);
                        }
                        return Promise.resolve();
                    }
                    // Firefox 68+ emits and processes {candidate: "", ...}, ignore
                    // in older versions.
                    if (arguments[0] && arguments[0].candidate === '') {
                        return Promise.resolve();
                    }
                    return nativeAddIceCandidate.apply(this, arguments);
                };
            }

            var modernStatsTypes = {
                inboundrtp: 'inbound-rtp',
                outboundrtp: 'outbound-rtp',
                candidatepair: 'candidate-pair',
                localcandidate: 'local-candidate',
                remotecandidate: 'remote-candidate'
            };

            var nativeGetStats = window.RTCPeerConnection.prototype.getStats;
            window.RTCPeerConnection.prototype.getStats = function getStats() {
                var _arguments = Array.prototype.slice.call(arguments),
                    selector = _arguments[0],
                    onSucc = _arguments[1],
                    onErr = _arguments[2];

                return nativeGetStats.apply(this, [selector || null]).then(function (stats) {
                    if (browserDetails.version < 53 && !onSucc) {
                        // Shim only promise getStats with spec-hyphens in type names
                        // Leave callback version alone; misc old uses of forEach before Map
                        try {
                            stats.forEach(function (stat) {
                                stat.type = modernStatsTypes[stat.type] || stat.type;
                            });
                        } catch (e) {
                            if (e.name !== 'TypeError') {
                                throw e;
                            }
                            // Avoid TypeError: "type" is read-only, in old versions. 34-43ish
                            stats.forEach(function (stat, i) {
                                stats.set(i, Object.assign({}, stat, {
                                    type: modernStatsTypes[stat.type] || stat.type
                                }));
                            });
                        }
                    }
                    return stats;
                }).then(onSucc, onErr);
            };
        }

        function shimSenderGetStats(window) {
            if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender)) {
                return;
            }
            if (window.RTCRtpSender && 'getStats' in window.RTCRtpSender.prototype) {
                return;
            }
            var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
            if (origGetSenders) {
                window.RTCPeerConnection.prototype.getSenders = function getSenders() {
                    var _this = this;

                    var senders = origGetSenders.apply(this, []);
                    senders.forEach(function (sender) {
                        return sender._pc = _this;
                    });
                    return senders;
                };
            }

            var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
            if (origAddTrack) {
                window.RTCPeerConnection.prototype.addTrack = function addTrack() {
                    var sender = origAddTrack.apply(this, arguments);
                    sender._pc = this;
                    return sender;
                };
            }
            window.RTCRtpSender.prototype.getStats = function getStats() {
                return this.track ? this._pc.getStats(this.track) : Promise.resolve(new Map());
            };
        }

        function shimReceiverGetStats(window) {
            if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection && window.RTCRtpSender)) {
                return;
            }
            if (window.RTCRtpSender && 'getStats' in window.RTCRtpReceiver.prototype) {
                return;
            }
            var origGetReceivers = window.RTCPeerConnection.prototype.getReceivers;
            if (origGetReceivers) {
                window.RTCPeerConnection.prototype.getReceivers = function getReceivers() {
                    var _this2 = this;

                    var receivers = origGetReceivers.apply(this, []);
                    receivers.forEach(function (receiver) {
                        return receiver._pc = _this2;
                    });
                    return receivers;
                };
            }
            utils.wrapPeerConnectionEvent(window, 'track', function (e) {
                e.receiver._pc = e.srcElement;
                return e;
            });
            window.RTCRtpReceiver.prototype.getStats = function getStats() {
                return this._pc.getStats(this.track);
            };
        }

        function shimRemoveStream(window) {
            if (!window.RTCPeerConnection || 'removeStream' in window.RTCPeerConnection.prototype) {
                return;
            }
            window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
                var _this3 = this;

                utils.deprecated('removeStream', 'removeTrack');
                this.getSenders().forEach(function (sender) {
                    if (sender.track && stream.getTracks().includes(sender.track)) {
                        _this3.removeTrack(sender);
                    }
                });
            };
        }

        function shimRTCDataChannel(window) {
            // rename DataChannel to RTCDataChannel (native fix in FF60):
            // https://bugzilla.mozilla.org/show_bug.cgi?id=1173851
            if (window.DataChannel && !window.RTCDataChannel) {
                window.RTCDataChannel = window.DataChannel;
            }
        }

        function shimAddTransceiver(window) {
            // https://github.com/webrtcHacks/adapter/issues/998#issuecomment-516921647
            // Firefox ignores the init sendEncodings options passed to addTransceiver
            // https://bugzilla.mozilla.org/show_bug.cgi?id=1396918
            if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection)) {
                return;
            }
            var origAddTransceiver = window.RTCPeerConnection.prototype.addTransceiver;
            if (origAddTransceiver) {
                window.RTCPeerConnection.prototype.addTransceiver = function addTransceiver() {
                    this.setParametersPromises = [];
                    var initParameters = arguments[1];
                    var shouldPerformCheck = initParameters && 'sendEncodings' in initParameters;
                    if (shouldPerformCheck) {
                        // If sendEncodings params are provided, validate grammar
                        initParameters.sendEncodings.forEach(function (encodingParam) {
                            if ('rid' in encodingParam) {
                                var ridRegex = /^[a-z0-9]{0,16}$/i;
                                if (!ridRegex.test(encodingParam.rid)) {
                                    throw new TypeError('Invalid RID value provided.');
                                }
                            }
                            if ('scaleResolutionDownBy' in encodingParam) {
                                if (!(parseFloat(encodingParam.scaleResolutionDownBy) >= 1.0)) {
                                    throw new RangeError('scale_resolution_down_by must be >= 1.0');
                                }
                            }
                            if ('maxFramerate' in encodingParam) {
                                if (!(parseFloat(encodingParam.maxFramerate) >= 0)) {
                                    throw new RangeError('max_framerate must be >= 0.0');
                                }
                            }
                        });
                    }
                    var transceiver = origAddTransceiver.apply(this, arguments);
                    if (shouldPerformCheck) {
                        // Check if the init options were applied. If not we do this in an
                        // asynchronous way and save the promise reference in a global object.
                        // This is an ugly hack, but at the same time is way more robust than
                        // checking the sender parameters before and after the createOffer
                        // Also note that after the createoffer we are not 100% sure that
                        // the params were asynchronously applied so we might miss the
                        // opportunity to recreate offer.
                        var sender = transceiver.sender;

                        var params = sender.getParameters();
                        if (!('encodings' in params) ||
                            // Avoid being fooled by patched getParameters() below.
                            params.encodings.length === 1 && Object.keys(params.encodings[0]).length === 0) {
                            params.encodings = initParameters.sendEncodings;
                            sender.sendEncodings = initParameters.sendEncodings;
                            this.setParametersPromises.push(sender.setParameters(params).then(function () {
                                delete sender.sendEncodings;
                            }).catch(function () {
                                delete sender.sendEncodings;
                            }));
                        }
                    }
                    return transceiver;
                };
            }
        }

        function shimGetParameters(window) {
            if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCRtpSender)) {
                return;
            }
            var origGetParameters = window.RTCRtpSender.prototype.getParameters;
            if (origGetParameters) {
                window.RTCRtpSender.prototype.getParameters = function getParameters() {
                    var params = origGetParameters.apply(this, arguments);
                    if (!('encodings' in params)) {
                        params.encodings = [].concat(this.sendEncodings || [{}]);
                    }
                    return params;
                };
            }
        }

        function shimCreateOffer(window) {
            // https://github.com/webrtcHacks/adapter/issues/998#issuecomment-516921647
            // Firefox ignores the init sendEncodings options passed to addTransceiver
            // https://bugzilla.mozilla.org/show_bug.cgi?id=1396918
            if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection)) {
                return;
            }
            var origCreateOffer = window.RTCPeerConnection.prototype.createOffer;
            window.RTCPeerConnection.prototype.createOffer = function createOffer() {
                var _this4 = this,
                    _arguments2 = arguments;

                if (this.setParametersPromises && this.setParametersPromises.length) {
                    return Promise.all(this.setParametersPromises).then(function () {
                        return origCreateOffer.apply(_this4, _arguments2);
                    }).finally(function () {
                        _this4.setParametersPromises = [];
                    });
                }
                return origCreateOffer.apply(this, arguments);
            };
        }

        function shimCreateAnswer(window) {
            // https://github.com/webrtcHacks/adapter/issues/998#issuecomment-516921647
            // Firefox ignores the init sendEncodings options passed to addTransceiver
            // https://bugzilla.mozilla.org/show_bug.cgi?id=1396918
            if (!((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCPeerConnection)) {
                return;
            }
            var origCreateAnswer = window.RTCPeerConnection.prototype.createAnswer;
            window.RTCPeerConnection.prototype.createAnswer = function createAnswer() {
                var _this5 = this,
                    _arguments3 = arguments;

                if (this.setParametersPromises && this.setParametersPromises.length) {
                    return Promise.all(this.setParametersPromises).then(function () {
                        return origCreateAnswer.apply(_this5, _arguments3);
                    }).finally(function () {
                        _this5.setParametersPromises = [];
                    });
                }
                return origCreateAnswer.apply(this, arguments);
            };
        }

    },{"../utils":15,"./getdisplaymedia":12,"./getusermedia":13}],12:[function(require,module,exports){
        /*
 *  Copyright (c) 2018 The adapter.js project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });
        exports.shimGetDisplayMedia = shimGetDisplayMedia;
        function shimGetDisplayMedia(window, preferredMediaSource) {
            if (window.navigator.mediaDevices && 'getDisplayMedia' in window.navigator.mediaDevices) {
                return;
            }
            if (!window.navigator.mediaDevices) {
                return;
            }
            window.navigator.mediaDevices.getDisplayMedia = function getDisplayMedia(constraints) {
                if (!(constraints && constraints.video)) {
                    var err = new DOMException('getDisplayMedia without video ' + 'constraints is undefined');
                    err.name = 'NotFoundError';
                    // from https://heycam.github.io/webidl/#idl-DOMException-error-names
                    err.code = 8;
                    return Promise.reject(err);
                }
                if (constraints.video === true) {
                    constraints.video = { mediaSource: preferredMediaSource };
                } else {
                    constraints.video.mediaSource = preferredMediaSource;
                }
                return window.navigator.mediaDevices.getUserMedia(constraints);
            };
        }

    },{}],13:[function(require,module,exports){
        /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });

        var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

        exports.shimGetUserMedia = shimGetUserMedia;

        var _utils = require('../utils');

        var utils = _interopRequireWildcard(_utils);

        function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

        function shimGetUserMedia(window) {
            var browserDetails = utils.detectBrowser(window);
            var navigator = window && window.navigator;
            var MediaStreamTrack = window && window.MediaStreamTrack;

            navigator.getUserMedia = function (constraints, onSuccess, onError) {
                // Replace Firefox 44+'s deprecation warning with unprefixed version.
                utils.deprecated('navigator.getUserMedia', 'navigator.mediaDevices.getUserMedia');
                navigator.mediaDevices.getUserMedia(constraints).then(onSuccess, onError);
            };

            if (!(browserDetails.version > 55 && 'autoGainControl' in navigator.mediaDevices.getSupportedConstraints())) {
                var remap = function remap(obj, a, b) {
                    if (a in obj && !(b in obj)) {
                        obj[b] = obj[a];
                        delete obj[a];
                    }
                };

                var nativeGetUserMedia = navigator.mediaDevices.getUserMedia.bind(navigator.mediaDevices);
                navigator.mediaDevices.getUserMedia = function (c) {
                    if ((typeof c === 'undefined' ? 'undefined' : _typeof(c)) === 'object' && _typeof(c.audio) === 'object') {
                        c = JSON.parse(JSON.stringify(c));
                        remap(c.audio, 'autoGainControl', 'mozAutoGainControl');
                        remap(c.audio, 'noiseSuppression', 'mozNoiseSuppression');
                    }
                    return nativeGetUserMedia(c);
                };

                if (MediaStreamTrack && MediaStreamTrack.prototype.getSettings) {
                    var nativeGetSettings = MediaStreamTrack.prototype.getSettings;
                    MediaStreamTrack.prototype.getSettings = function () {
                        var obj = nativeGetSettings.apply(this, arguments);
                        remap(obj, 'mozAutoGainControl', 'autoGainControl');
                        remap(obj, 'mozNoiseSuppression', 'noiseSuppression');
                        return obj;
                    };
                }

                if (MediaStreamTrack && MediaStreamTrack.prototype.applyConstraints) {
                    var nativeApplyConstraints = MediaStreamTrack.prototype.applyConstraints;
                    MediaStreamTrack.prototype.applyConstraints = function (c) {
                        if (this.kind === 'audio' && (typeof c === 'undefined' ? 'undefined' : _typeof(c)) === 'object') {
                            c = JSON.parse(JSON.stringify(c));
                            remap(c, 'autoGainControl', 'mozAutoGainControl');
                            remap(c, 'noiseSuppression', 'mozNoiseSuppression');
                        }
                        return nativeApplyConstraints.apply(this, [c]);
                    };
                }
            }
        }

    },{"../utils":15}],14:[function(require,module,exports){
        /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });

        var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

        exports.shimLocalStreamsAPI = shimLocalStreamsAPI;
        exports.shimRemoteStreamsAPI = shimRemoteStreamsAPI;
        exports.shimCallbacksAPI = shimCallbacksAPI;
        exports.shimGetUserMedia = shimGetUserMedia;
        exports.shimConstraints = shimConstraints;
        exports.shimRTCIceServerUrls = shimRTCIceServerUrls;
        exports.shimTrackEventTransceiver = shimTrackEventTransceiver;
        exports.shimCreateOfferLegacy = shimCreateOfferLegacy;
        exports.shimAudioContext = shimAudioContext;

        var _utils = require('../utils');

        var utils = _interopRequireWildcard(_utils);

        function _interopRequireWildcard(obj) { if (obj && obj.__esModule) { return obj; } else { var newObj = {}; if (obj != null) { for (var key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) newObj[key] = obj[key]; } } newObj.default = obj; return newObj; } }

        function shimLocalStreamsAPI(window) {
            if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
                return;
            }
            if (!('getLocalStreams' in window.RTCPeerConnection.prototype)) {
                window.RTCPeerConnection.prototype.getLocalStreams = function getLocalStreams() {
                    if (!this._localStreams) {
                        this._localStreams = [];
                    }
                    return this._localStreams;
                };
            }
            if (!('addStream' in window.RTCPeerConnection.prototype)) {
                var _addTrack = window.RTCPeerConnection.prototype.addTrack;
                window.RTCPeerConnection.prototype.addStream = function addStream(stream) {
                    var _this = this;

                    if (!this._localStreams) {
                        this._localStreams = [];
                    }
                    if (!this._localStreams.includes(stream)) {
                        this._localStreams.push(stream);
                    }
                    // Try to emulate Chrome's behaviour of adding in audio-video order.
                    // Safari orders by track id.
                    stream.getAudioTracks().forEach(function (track) {
                        return _addTrack.call(_this, track, stream);
                    });
                    stream.getVideoTracks().forEach(function (track) {
                        return _addTrack.call(_this, track, stream);
                    });
                };

                window.RTCPeerConnection.prototype.addTrack = function addTrack(track) {
                    var _this2 = this;

                    for (var _len = arguments.length, streams = Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
                        streams[_key - 1] = arguments[_key];
                    }

                    if (streams) {
                        streams.forEach(function (stream) {
                            if (!_this2._localStreams) {
                                _this2._localStreams = [stream];
                            } else if (!_this2._localStreams.includes(stream)) {
                                _this2._localStreams.push(stream);
                            }
                        });
                    }
                    return _addTrack.apply(this, arguments);
                };
            }
            if (!('removeStream' in window.RTCPeerConnection.prototype)) {
                window.RTCPeerConnection.prototype.removeStream = function removeStream(stream) {
                    var _this3 = this;

                    if (!this._localStreams) {
                        this._localStreams = [];
                    }
                    var index = this._localStreams.indexOf(stream);
                    if (index === -1) {
                        return;
                    }
                    this._localStreams.splice(index, 1);
                    var tracks = stream.getTracks();
                    this.getSenders().forEach(function (sender) {
                        if (tracks.includes(sender.track)) {
                            _this3.removeTrack(sender);
                        }
                    });
                };
            }
        }

        function shimRemoteStreamsAPI(window) {
            if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
                return;
            }
            if (!('getRemoteStreams' in window.RTCPeerConnection.prototype)) {
                window.RTCPeerConnection.prototype.getRemoteStreams = function getRemoteStreams() {
                    return this._remoteStreams ? this._remoteStreams : [];
                };
            }
            if (!('onaddstream' in window.RTCPeerConnection.prototype)) {
                Object.defineProperty(window.RTCPeerConnection.prototype, 'onaddstream', {
                    get: function get() {
                        return this._onaddstream;
                    },
                    set: function set(f) {
                        var _this4 = this;

                        if (this._onaddstream) {
                            this.removeEventListener('addstream', this._onaddstream);
                            this.removeEventListener('track', this._onaddstreampoly);
                        }
                        this.addEventListener('addstream', this._onaddstream = f);
                        this.addEventListener('track', this._onaddstreampoly = function (e) {
                            e.streams.forEach(function (stream) {
                                if (!_this4._remoteStreams) {
                                    _this4._remoteStreams = [];
                                }
                                if (_this4._remoteStreams.includes(stream)) {
                                    return;
                                }
                                _this4._remoteStreams.push(stream);
                                var event = new Event('addstream');
                                event.stream = stream;
                                _this4.dispatchEvent(event);
                            });
                        });
                    }
                });
                var origSetRemoteDescription = window.RTCPeerConnection.prototype.setRemoteDescription;
                window.RTCPeerConnection.prototype.setRemoteDescription = function setRemoteDescription() {
                    var pc = this;
                    if (!this._onaddstreampoly) {
                        this.addEventListener('track', this._onaddstreampoly = function (e) {
                            e.streams.forEach(function (stream) {
                                if (!pc._remoteStreams) {
                                    pc._remoteStreams = [];
                                }
                                if (pc._remoteStreams.indexOf(stream) >= 0) {
                                    return;
                                }
                                pc._remoteStreams.push(stream);
                                var event = new Event('addstream');
                                event.stream = stream;
                                pc.dispatchEvent(event);
                            });
                        });
                    }
                    return origSetRemoteDescription.apply(pc, arguments);
                };
            }
        }

        function shimCallbacksAPI(window) {
            if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || !window.RTCPeerConnection) {
                return;
            }
            var prototype = window.RTCPeerConnection.prototype;
            var origCreateOffer = prototype.createOffer;
            var origCreateAnswer = prototype.createAnswer;
            var setLocalDescription = prototype.setLocalDescription;
            var setRemoteDescription = prototype.setRemoteDescription;
            var addIceCandidate = prototype.addIceCandidate;

            prototype.createOffer = function createOffer(successCallback, failureCallback) {
                var options = arguments.length >= 2 ? arguments[2] : arguments[0];
                var promise = origCreateOffer.apply(this, [options]);
                if (!failureCallback) {
                    return promise;
                }
                promise.then(successCallback, failureCallback);
                return Promise.resolve();
            };

            prototype.createAnswer = function createAnswer(successCallback, failureCallback) {
                var options = arguments.length >= 2 ? arguments[2] : arguments[0];
                var promise = origCreateAnswer.apply(this, [options]);
                if (!failureCallback) {
                    return promise;
                }
                promise.then(successCallback, failureCallback);
                return Promise.resolve();
            };

            var withCallback = function withCallback(description, successCallback, failureCallback) {
                var promise = setLocalDescription.apply(this, [description]);
                if (!failureCallback) {
                    return promise;
                }
                promise.then(successCallback, failureCallback);
                return Promise.resolve();
            };
            prototype.setLocalDescription = withCallback;

            withCallback = function withCallback(description, successCallback, failureCallback) {
                var promise = setRemoteDescription.apply(this, [description]);
                if (!failureCallback) {
                    return promise;
                }
                promise.then(successCallback, failureCallback);
                return Promise.resolve();
            };
            prototype.setRemoteDescription = withCallback;

            withCallback = function withCallback(candidate, successCallback, failureCallback) {
                var promise = addIceCandidate.apply(this, [candidate]);
                if (!failureCallback) {
                    return promise;
                }
                promise.then(successCallback, failureCallback);
                return Promise.resolve();
            };
            prototype.addIceCandidate = withCallback;
        }

        function shimGetUserMedia(window) {
            var navigator = window && window.navigator;

            if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
                // shim not needed in Safari 12.1
                var mediaDevices = navigator.mediaDevices;
                var _getUserMedia = mediaDevices.getUserMedia.bind(mediaDevices);
                navigator.mediaDevices.getUserMedia = function (constraints) {
                    return _getUserMedia(shimConstraints(constraints));
                };
            }

            if (!navigator.getUserMedia && navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
                navigator.getUserMedia = function getUserMedia(constraints, cb, errcb) {
                    navigator.mediaDevices.getUserMedia(constraints).then(cb, errcb);
                }.bind(navigator);
            }
        }

        function shimConstraints(constraints) {
            if (constraints && constraints.video !== undefined) {
                return Object.assign({}, constraints, { video: utils.compactObject(constraints.video) });
            }

            return constraints;
        }

        function shimRTCIceServerUrls(window) {
            if (!window.RTCPeerConnection) {
                return;
            }
            // migrate from non-spec RTCIceServer.url to RTCIceServer.urls
            var OrigPeerConnection = window.RTCPeerConnection;
            window.RTCPeerConnection = function RTCPeerConnection(pcConfig, pcConstraints) {
                if (pcConfig && pcConfig.iceServers) {
                    var newIceServers = [];
                    for (var i = 0; i < pcConfig.iceServers.length; i++) {
                        var server = pcConfig.iceServers[i];
                        if (!server.hasOwnProperty('urls') && server.hasOwnProperty('url')) {
                            utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
                            server = JSON.parse(JSON.stringify(server));
                            server.urls = server.url;
                            delete server.url;
                            newIceServers.push(server);
                        } else {
                            newIceServers.push(pcConfig.iceServers[i]);
                        }
                    }
                    pcConfig.iceServers = newIceServers;
                }
                return new OrigPeerConnection(pcConfig, pcConstraints);
            };
            window.RTCPeerConnection.prototype = OrigPeerConnection.prototype;
            // wrap static methods. Currently just generateCertificate.
            if ('generateCertificate' in OrigPeerConnection) {
                Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
                    get: function get() {
                        return OrigPeerConnection.generateCertificate;
                    }
                });
            }
        }

        function shimTrackEventTransceiver(window) {
            // Add event.transceiver member over deprecated event.receiver
            if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object' && window.RTCTrackEvent && 'receiver' in window.RTCTrackEvent.prototype && !('transceiver' in window.RTCTrackEvent.prototype)) {
                Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
                    get: function get() {
                        return { receiver: this.receiver };
                    }
                });
            }
        }

        function shimCreateOfferLegacy(window) {
            var origCreateOffer = window.RTCPeerConnection.prototype.createOffer;
            window.RTCPeerConnection.prototype.createOffer = function createOffer(offerOptions) {
                if (offerOptions) {
                    if (typeof offerOptions.offerToReceiveAudio !== 'undefined') {
                        // support bit values
                        offerOptions.offerToReceiveAudio = !!offerOptions.offerToReceiveAudio;
                    }
                    var audioTransceiver = this.getTransceivers().find(function (transceiver) {
                        return transceiver.receiver.track.kind === 'audio';
                    });
                    if (offerOptions.offerToReceiveAudio === false && audioTransceiver) {
                        if (audioTransceiver.direction === 'sendrecv') {
                            if (audioTransceiver.setDirection) {
                                audioTransceiver.setDirection('sendonly');
                            } else {
                                audioTransceiver.direction = 'sendonly';
                            }
                        } else if (audioTransceiver.direction === 'recvonly') {
                            if (audioTransceiver.setDirection) {
                                audioTransceiver.setDirection('inactive');
                            } else {
                                audioTransceiver.direction = 'inactive';
                            }
                        }
                    } else if (offerOptions.offerToReceiveAudio === true && !audioTransceiver) {
                        this.addTransceiver('audio');
                    }

                    if (typeof offerOptions.offerToReceiveVideo !== 'undefined') {
                        // support bit values
                        offerOptions.offerToReceiveVideo = !!offerOptions.offerToReceiveVideo;
                    }
                    var videoTransceiver = this.getTransceivers().find(function (transceiver) {
                        return transceiver.receiver.track.kind === 'video';
                    });
                    if (offerOptions.offerToReceiveVideo === false && videoTransceiver) {
                        if (videoTransceiver.direction === 'sendrecv') {
                            if (videoTransceiver.setDirection) {
                                videoTransceiver.setDirection('sendonly');
                            } else {
                                videoTransceiver.direction = 'sendonly';
                            }
                        } else if (videoTransceiver.direction === 'recvonly') {
                            if (videoTransceiver.setDirection) {
                                videoTransceiver.setDirection('inactive');
                            } else {
                                videoTransceiver.direction = 'inactive';
                            }
                        }
                    } else if (offerOptions.offerToReceiveVideo === true && !videoTransceiver) {
                        this.addTransceiver('video');
                    }
                }
                return origCreateOffer.apply(this, arguments);
            };
        }

        function shimAudioContext(window) {
            if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) !== 'object' || window.AudioContext) {
                return;
            }
            window.AudioContext = window.webkitAudioContext;
        }

    },{"../utils":15}],15:[function(require,module,exports){
        /*
 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        Object.defineProperty(exports, "__esModule", {
            value: true
        });

        var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol" ? function (obj) { return typeof obj; } : function (obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; };

        exports.extractVersion = extractVersion;
        exports.wrapPeerConnectionEvent = wrapPeerConnectionEvent;
        exports.disableLog = disableLog;
        exports.disableWarnings = disableWarnings;
        exports.log = log;
        exports.deprecated = deprecated;
        exports.detectBrowser = detectBrowser;
        exports.compactObject = compactObject;
        exports.walkStats = walkStats;
        exports.filterStats = filterStats;

        function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }

        var logDisabled_ = true;
        var deprecationWarnings_ = true;

        /**
         * Extract browser version out of the provided user agent string.
         *
         * @param {!string} uastring userAgent string.
         * @param {!string} expr Regular expression used as match criteria.
         * @param {!number} pos position in the version string to be returned.
         * @return {!number} browser version.
         */
        function extractVersion(uastring, expr, pos) {
            var match = uastring.match(expr);
            return match && match.length >= pos && parseInt(match[pos], 10);
        }

// Wraps the peerconnection event eventNameToWrap in a function
// which returns the modified event object (or false to prevent
// the event).
        function wrapPeerConnectionEvent(window, eventNameToWrap, wrapper) {
            if (!window.RTCPeerConnection) {
                return;
            }
            var proto = window.RTCPeerConnection.prototype;
            var nativeAddEventListener = proto.addEventListener;
            proto.addEventListener = function (nativeEventName, cb) {
                if (nativeEventName !== eventNameToWrap) {
                    return nativeAddEventListener.apply(this, arguments);
                }
                var wrappedCallback = function wrappedCallback(e) {
                    var modifiedEvent = wrapper(e);
                    if (modifiedEvent) {
                        if (cb.handleEvent) {
                            cb.handleEvent(modifiedEvent);
                        } else {
                            cb(modifiedEvent);
                        }
                    }
                };
                this._eventMap = this._eventMap || {};
                if (!this._eventMap[eventNameToWrap]) {
                    this._eventMap[eventNameToWrap] = new Map();
                }
                this._eventMap[eventNameToWrap].set(cb, wrappedCallback);
                return nativeAddEventListener.apply(this, [nativeEventName, wrappedCallback]);
            };

            var nativeRemoveEventListener = proto.removeEventListener;
            proto.removeEventListener = function (nativeEventName, cb) {
                if (nativeEventName !== eventNameToWrap || !this._eventMap || !this._eventMap[eventNameToWrap]) {
                    return nativeRemoveEventListener.apply(this, arguments);
                }
                if (!this._eventMap[eventNameToWrap].has(cb)) {
                    return nativeRemoveEventListener.apply(this, arguments);
                }
                var unwrappedCb = this._eventMap[eventNameToWrap].get(cb);
                this._eventMap[eventNameToWrap].delete(cb);
                if (this._eventMap[eventNameToWrap].size === 0) {
                    delete this._eventMap[eventNameToWrap];
                }
                if (Object.keys(this._eventMap).length === 0) {
                    delete this._eventMap;
                }
                return nativeRemoveEventListener.apply(this, [nativeEventName, unwrappedCb]);
            };

            Object.defineProperty(proto, 'on' + eventNameToWrap, {
                get: function get() {
                    return this['_on' + eventNameToWrap];
                },
                set: function set(cb) {
                    if (this['_on' + eventNameToWrap]) {
                        this.removeEventListener(eventNameToWrap, this['_on' + eventNameToWrap]);
                        delete this['_on' + eventNameToWrap];
                    }
                    if (cb) {
                        this.addEventListener(eventNameToWrap, this['_on' + eventNameToWrap] = cb);
                    }
                },

                enumerable: true,
                configurable: true
            });
        }

        function disableLog(bool) {
            if (typeof bool !== 'boolean') {
                return new Error('Argument type: ' + (typeof bool === 'undefined' ? 'undefined' : _typeof(bool)) + '. Please use a boolean.');
            }
            logDisabled_ = bool;
            return bool ? 'adapter.js logging disabled' : 'adapter.js logging enabled';
        }

        /**
         * Disable or enable deprecation warnings
         * @param {!boolean} bool set to true to disable warnings.
         */
        function disableWarnings(bool) {
            if (typeof bool !== 'boolean') {
                return new Error('Argument type: ' + (typeof bool === 'undefined' ? 'undefined' : _typeof(bool)) + '. Please use a boolean.');
            }
            deprecationWarnings_ = !bool;
            return 'adapter.js deprecation warnings ' + (bool ? 'disabled' : 'enabled');
        }

        function log() {
            if ((typeof window === 'undefined' ? 'undefined' : _typeof(window)) === 'object') {
                if (logDisabled_) {
                    return;
                }
                if (typeof console !== 'undefined' && typeof console.log === 'function') {
                    console.log.apply(console, arguments);
                }
            }
        }

        /**
         * Shows a deprecation warning suggesting the modern and spec-compatible API.
         */
        function deprecated(oldMethod, newMethod) {
            if (!deprecationWarnings_) {
                return;
            }
            console.warn(oldMethod + ' is deprecated, please use ' + newMethod + ' instead.');
        }

        /**
         * Browser detector.
         *
         * @return {object} result containing browser and version
         *     properties.
         */
        function detectBrowser(window) {
            // Returned result object.
            var result = { browser: null, version: null };

            // Fail early if it's not a browser
            if (typeof window === 'undefined' || !window.navigator) {
                result.browser = 'Not a browser.';
                return result;
            }

            var navigator = window.navigator;


            if (navigator.mozGetUserMedia) {
                // Firefox.
                result.browser = 'firefox';
                result.version = extractVersion(navigator.userAgent, /Firefox\/(\d+)\./, 1);
            } else if (navigator.webkitGetUserMedia || window.isSecureContext === false && window.webkitRTCPeerConnection && !window.RTCIceGatherer) {
                // Chrome, Chromium, Webview, Opera.
                // Version matches Chrome/WebRTC version.
                // Chrome 74 removed webkitGetUserMedia on http as well so we need the
                // more complicated fallback to webkitRTCPeerConnection.
                result.browser = 'chrome';
                result.version = extractVersion(navigator.userAgent, /Chrom(e|ium)\/(\d+)\./, 2);
            } else if (navigator.mediaDevices && navigator.userAgent.match(/Edge\/(\d+).(\d+)$/)) {
                // Edge.
                result.browser = 'edge';
                result.version = extractVersion(navigator.userAgent, /Edge\/(\d+).(\d+)$/, 2);
            } else if (window.RTCPeerConnection && navigator.userAgent.match(/AppleWebKit\/(\d+)\./)) {
                // Safari.
                result.browser = 'safari';
                result.version = extractVersion(navigator.userAgent, /AppleWebKit\/(\d+)\./, 1);
                result.supportsUnifiedPlan = window.RTCRtpTransceiver && 'currentDirection' in window.RTCRtpTransceiver.prototype;
            } else {
                // Default fallthrough: not supported.
                result.browser = 'Not a supported browser.';
                return result;
            }

            return result;
        }

        /**
         * Checks if something is an object.
         *
         * @param {*} val The something you want to check.
         * @return true if val is an object, false otherwise.
         */
        function isObject(val) {
            return Object.prototype.toString.call(val) === '[object Object]';
        }

        /**
         * Remove all empty objects and undefined values
         * from a nested object -- an enhanced and vanilla version
         * of Lodash's `compact`.
         */
        function compactObject(data) {
            if (!isObject(data)) {
                return data;
            }

            return Object.keys(data).reduce(function (accumulator, key) {
                var isObj = isObject(data[key]);
                var value = isObj ? compactObject(data[key]) : data[key];
                var isEmptyObject = isObj && !Object.keys(value).length;
                if (value === undefined || isEmptyObject) {
                    return accumulator;
                }
                return Object.assign(accumulator, _defineProperty({}, key, value));
            }, {});
        }

        /* iterates the stats graph recursively. */
        function walkStats(stats, base, resultSet) {
            if (!base || resultSet.has(base.id)) {
                return;
            }
            resultSet.set(base.id, base);
            Object.keys(base).forEach(function (name) {
                if (name.endsWith('Id')) {
                    walkStats(stats, stats.get(base[name]), resultSet);
                } else if (name.endsWith('Ids')) {
                    base[name].forEach(function (id) {
                        walkStats(stats, stats.get(id), resultSet);
                    });
                }
            });
        }

        /* filter getStats for a sender/receiver track. */
        function filterStats(result, track, outbound) {
            var streamStatsType = outbound ? 'outbound-rtp' : 'inbound-rtp';
            var filteredResult = new Map();
            if (track === null) {
                return filteredResult;
            }
            var trackStats = [];
            result.forEach(function (value) {
                if (value.type === 'track' && value.trackIdentifier === track.id) {
                    trackStats.push(value);
                }
            });
            trackStats.forEach(function (trackStat) {
                result.forEach(function (stats) {
                    if (stats.type === streamStatsType && stats.trackId === trackStat.id) {
                        walkStats(result, stats, filteredResult);
                    }
                });
            });
            return filteredResult;
        }

    },{}],16:[function(require,module,exports){
        /*
 *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree.
 */
        /* eslint-env node */
        'use strict';

        var SDPUtils = require('sdp');

        function fixStatsType(stat) {
            return {
                inboundrtp: 'inbound-rtp',
                outboundrtp: 'outbound-rtp',
                candidatepair: 'candidate-pair',
                localcandidate: 'local-candidate',
                remotecandidate: 'remote-candidate'
            }[stat.type] || stat.type;
        }

        function writeMediaSection(transceiver, caps, type, stream, dtlsRole) {
            var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);

            // Map ICE parameters (ufrag, pwd) to SDP.
            sdp += SDPUtils.writeIceParameters(
                transceiver.iceGatherer.getLocalParameters());

            // Map DTLS parameters to SDP.
            sdp += SDPUtils.writeDtlsParameters(
                transceiver.dtlsTransport.getLocalParameters(),
                type === 'offer' ? 'actpass' : dtlsRole || 'active');

            sdp += 'a=mid:' + transceiver.mid + '\r\n';

            if (transceiver.rtpSender && transceiver.rtpReceiver) {
                sdp += 'a=sendrecv\r\n';
            } else if (transceiver.rtpSender) {
                sdp += 'a=sendonly\r\n';
            } else if (transceiver.rtpReceiver) {
                sdp += 'a=recvonly\r\n';
            } else {
                sdp += 'a=inactive\r\n';
            }

            if (transceiver.rtpSender) {
                var trackId = transceiver.rtpSender._initialTrackId ||
                    transceiver.rtpSender.track.id;
                transceiver.rtpSender._initialTrackId = trackId;
                // spec.
                var msid = 'msid:' + (stream ? stream.id : '-') + ' ' +
                    trackId + '\r\n';
                sdp += 'a=' + msid;
                // for Chrome. Legacy should no longer be required.
                sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
                    ' ' + msid;

                // RTX
                if (transceiver.sendEncodingParameters[0].rtx) {
                    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                        ' ' + msid;
                    sdp += 'a=ssrc-group:FID ' +
                        transceiver.sendEncodingParameters[0].ssrc + ' ' +
                        transceiver.sendEncodingParameters[0].rtx.ssrc +
                        '\r\n';
                }
            }
            // FIXME: this should be written by writeRtpDescription.
            sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
                ' cname:' + SDPUtils.localCName + '\r\n';
            if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
                sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                    ' cname:' + SDPUtils.localCName + '\r\n';
            }
            return sdp;
        }

// Edge does not like
// 1) stun: filtered after 14393 unless ?transport=udp is present
// 2) turn: that does not have all of turn:host:port?transport=udp
// 3) turn: with ipv6 addresses
// 4) turn: occurring muliple times
        function filterIceServers(iceServers, edgeVersion) {
            var hasTurn = false;
            iceServers = JSON.parse(JSON.stringify(iceServers));
            return iceServers.filter(function(server) {
                if (server && (server.urls || server.url)) {
                    var urls = server.urls || server.url;
                    if (server.url && !server.urls) {
                        console.warn('RTCIceServer.url is deprecated! Use urls instead.');
                    }
                    var isString = typeof urls === 'string';
                    if (isString) {
                        urls = [urls];
                    }
                    urls = urls.filter(function(url) {
                        var validTurn = url.indexOf('turn:') === 0 &&
                            url.indexOf('transport=udp') !== -1 &&
                            url.indexOf('turn:[') === -1 &&
                            !hasTurn;

                        if (validTurn) {
                            hasTurn = true;
                            return true;
                        }
                        return url.indexOf('stun:') === 0 && edgeVersion >= 14393 &&
                            url.indexOf('?transport=udp') === -1;
                    });

                    delete server.url;
                    server.urls = isString ? urls[0] : urls;
                    return !!urls.length;
                }
            });
        }

// Determines the intersection of local and remote capabilities.
        function getCommonCapabilities(localCapabilities, remoteCapabilities) {
            var commonCapabilities = {
                codecs: [],
                headerExtensions: [],
                fecMechanisms: []
            };

            var findCodecByPayloadType = function(pt, codecs) {
                pt = parseInt(pt, 10);
                for (var i = 0; i < codecs.length; i++) {
                    if (codecs[i].payloadType === pt ||
                        codecs[i].preferredPayloadType === pt) {
                        return codecs[i];
                    }
                }
            };

            var rtxCapabilityMatches = function(lRtx, rRtx, lCodecs, rCodecs) {
                var lCodec = findCodecByPayloadType(lRtx.parameters.apt, lCodecs);
                var rCodec = findCodecByPayloadType(rRtx.parameters.apt, rCodecs);
                return lCodec && rCodec &&
                    lCodec.name.toLowerCase() === rCodec.name.toLowerCase();
            };

            localCapabilities.codecs.forEach(function(lCodec) {
                for (var i = 0; i < remoteCapabilities.codecs.length; i++) {
                    var rCodec = remoteCapabilities.codecs[i];
                    if (lCodec.name.toLowerCase() === rCodec.name.toLowerCase() &&
                        lCodec.clockRate === rCodec.clockRate) {
                        if (lCodec.name.toLowerCase() === 'rtx' &&
                            lCodec.parameters && rCodec.parameters.apt) {
                            // for RTX we need to find the local rtx that has a apt
                            // which points to the same local codec as the remote one.
                            if (!rtxCapabilityMatches(lCodec, rCodec,
                                localCapabilities.codecs, remoteCapabilities.codecs)) {
                                continue;
                            }
                        }
                        rCodec = JSON.parse(JSON.stringify(rCodec)); // deepcopy
                        // number of channels is the highest common number of channels
                        rCodec.numChannels = Math.min(lCodec.numChannels,
                            rCodec.numChannels);
                        // push rCodec so we reply with offerer payload type
                        commonCapabilities.codecs.push(rCodec);

                        // determine common feedback mechanisms
                        rCodec.rtcpFeedback = rCodec.rtcpFeedback.filter(function(fb) {
                            for (var j = 0; j < lCodec.rtcpFeedback.length; j++) {
                                if (lCodec.rtcpFeedback[j].type === fb.type &&
                                    lCodec.rtcpFeedback[j].parameter === fb.parameter) {
                                    return true;
                                }
                            }
                            return false;
                        });
                        // FIXME: also need to determine .parameters
                        //  see https://github.com/openpeer/ortc/issues/569
                        break;
                    }
                }
            });

            localCapabilities.headerExtensions.forEach(function(lHeaderExtension) {
                for (var i = 0; i < remoteCapabilities.headerExtensions.length;
                     i++) {
                    var rHeaderExtension = remoteCapabilities.headerExtensions[i];
                    if (lHeaderExtension.uri === rHeaderExtension.uri) {
                        commonCapabilities.headerExtensions.push(rHeaderExtension);
                        break;
                    }
                }
            });

            // FIXME: fecMechanisms
            return commonCapabilities;
        }

// is action=setLocalDescription with type allowed in signalingState
        function isActionAllowedInSignalingState(action, type, signalingState) {
            return {
                offer: {
                    setLocalDescription: ['stable', 'have-local-offer'],
                    setRemoteDescription: ['stable', 'have-remote-offer']
                },
                answer: {
                    setLocalDescription: ['have-remote-offer', 'have-local-pranswer'],
                    setRemoteDescription: ['have-local-offer', 'have-remote-pranswer']
                }
            }[type][action].indexOf(signalingState) !== -1;
        }

        function maybeAddCandidate(iceTransport, candidate) {
            // Edge's internal representation adds some fields therefore
            // not all fieldѕ are taken into account.
            var alreadyAdded = iceTransport.getRemoteCandidates()
                .find(function(remoteCandidate) {
                    return candidate.foundation === remoteCandidate.foundation &&
                        candidate.ip === remoteCandidate.ip &&
                        candidate.port === remoteCandidate.port &&
                        candidate.priority === remoteCandidate.priority &&
                        candidate.protocol === remoteCandidate.protocol &&
                        candidate.type === remoteCandidate.type;
                });
            if (!alreadyAdded) {
                iceTransport.addRemoteCandidate(candidate);
            }
            return !alreadyAdded;
        }


        function makeError(name, description) {
            var e = new Error(description);
            e.name = name;
            // legacy error codes from https://heycam.github.io/webidl/#idl-DOMException-error-names
            e.code = {
                NotSupportedError: 9,
                InvalidStateError: 11,
                InvalidAccessError: 15,
                TypeError: undefined,
                OperationError: undefined
            }[name];
            return e;
        }

        module.exports = function(window, edgeVersion) {
            // https://w3c.github.io/mediacapture-main/#mediastream
            // Helper function to add the track to the stream and
            // dispatch the event ourselves.
            function addTrackToStreamAndFireEvent(track, stream) {
                stream.addTrack(track);
                stream.dispatchEvent(new window.MediaStreamTrackEvent('addtrack',
                    {track: track}));
            }

            function removeTrackFromStreamAndFireEvent(track, stream) {
                stream.removeTrack(track);
                stream.dispatchEvent(new window.MediaStreamTrackEvent('removetrack',
                    {track: track}));
            }

            function fireAddTrack(pc, track, receiver, streams) {
                var trackEvent = new Event('track');
                trackEvent.track = track;
                trackEvent.receiver = receiver;
                trackEvent.transceiver = {receiver: receiver};
                trackEvent.streams = streams;
                window.setTimeout(function() {
                    pc._dispatchEvent('track', trackEvent);
                });
            }

            var RTCPeerConnection = function(config) {
                var pc = this;

                var _eventTarget = document.createDocumentFragment();
                ['addEventListener', 'removeEventListener', 'dispatchEvent']
                    .forEach(function(method) {
                        pc[method] = _eventTarget[method].bind(_eventTarget);
                    });

                this.canTrickleIceCandidates = null;

                this.needNegotiation = false;

                this.localStreams = [];
                this.remoteStreams = [];

                this._localDescription = null;
                this._remoteDescription = null;

                this.signalingState = 'stable';
                this.iceConnectionState = 'new';
                this.connectionState = 'new';
                this.iceGatheringState = 'new';

                config = JSON.parse(JSON.stringify(config || {}));

                this.usingBundle = config.bundlePolicy === 'max-bundle';
                if (config.rtcpMuxPolicy === 'negotiate') {
                    throw(makeError('NotSupportedError',
                        'rtcpMuxPolicy \'negotiate\' is not supported'));
                } else if (!config.rtcpMuxPolicy) {
                    config.rtcpMuxPolicy = 'require';
                }

                switch (config.iceTransportPolicy) {
                    case 'all':
                    case 'relay':
                        break;
                    default:
                        config.iceTransportPolicy = 'all';
                        break;
                }

                switch (config.bundlePolicy) {
                    case 'balanced':
                    case 'max-compat':
                    case 'max-bundle':
                        break;
                    default:
                        config.bundlePolicy = 'balanced';
                        break;
                }

                config.iceServers = filterIceServers(config.iceServers || [], edgeVersion);

                this._iceGatherers = [];
                if (config.iceCandidatePoolSize) {
                    for (var i = config.iceCandidatePoolSize; i > 0; i--) {
                        this._iceGatherers.push(new window.RTCIceGatherer({
                            iceServers: config.iceServers,
                            gatherPolicy: config.iceTransportPolicy
                        }));
                    }
                } else {
                    config.iceCandidatePoolSize = 0;
                }

                this._config = config;

                // per-track iceGathers, iceTransports, dtlsTransports, rtpSenders, ...
                // everything that is needed to describe a SDP m-line.
                this.transceivers = [];

                this._sdpSessionId = SDPUtils.generateSessionId();
                this._sdpSessionVersion = 0;

                this._dtlsRole = undefined; // role for a=setup to use in answers.

                this._isClosed = false;
            };

            Object.defineProperty(RTCPeerConnection.prototype, 'localDescription', {
                configurable: true,
                get: function() {
                    return this._localDescription;
                }
            });
            Object.defineProperty(RTCPeerConnection.prototype, 'remoteDescription', {
                configurable: true,
                get: function() {
                    return this._remoteDescription;
                }
            });

            // set up event handlers on prototype
            RTCPeerConnection.prototype.onicecandidate = null;
            RTCPeerConnection.prototype.onaddstream = null;
            RTCPeerConnection.prototype.ontrack = null;
            RTCPeerConnection.prototype.onremovestream = null;
            RTCPeerConnection.prototype.onsignalingstatechange = null;
            RTCPeerConnection.prototype.oniceconnectionstatechange = null;
            RTCPeerConnection.prototype.onconnectionstatechange = null;
            RTCPeerConnection.prototype.onicegatheringstatechange = null;
            RTCPeerConnection.prototype.onnegotiationneeded = null;
            RTCPeerConnection.prototype.ondatachannel = null;

            RTCPeerConnection.prototype._dispatchEvent = function(name, event) {
                if (this._isClosed) {
                    return;
                }
                this.dispatchEvent(event);
                if (typeof this['on' + name] === 'function') {
                    this['on' + name](event);
                }
            };

            RTCPeerConnection.prototype._emitGatheringStateChange = function() {
                var event = new Event('icegatheringstatechange');
                this._dispatchEvent('icegatheringstatechange', event);
            };

            RTCPeerConnection.prototype.getConfiguration = function() {
                return this._config;
            };

            RTCPeerConnection.prototype.getLocalStreams = function() {
                return this.localStreams;
            };

            RTCPeerConnection.prototype.getRemoteStreams = function() {
                return this.remoteStreams;
            };

            // internal helper to create a transceiver object.
            // (which is not yet the same as the WebRTC 1.0 transceiver)
            RTCPeerConnection.prototype._createTransceiver = function(kind, doNotAdd) {
                var hasBundleTransport = this.transceivers.length > 0;
                var transceiver = {
                    track: null,
                    iceGatherer: null,
                    iceTransport: null,
                    dtlsTransport: null,
                    localCapabilities: null,
                    remoteCapabilities: null,
                    rtpSender: null,
                    rtpReceiver: null,
                    kind: kind,
                    mid: null,
                    sendEncodingParameters: null,
                    recvEncodingParameters: null,
                    stream: null,
                    associatedRemoteMediaStreams: [],
                    wantReceive: true
                };
                if (this.usingBundle && hasBundleTransport) {
                    transceiver.iceTransport = this.transceivers[0].iceTransport;
                    transceiver.dtlsTransport = this.transceivers[0].dtlsTransport;
                } else {
                    var transports = this._createIceAndDtlsTransports();
                    transceiver.iceTransport = transports.iceTransport;
                    transceiver.dtlsTransport = transports.dtlsTransport;
                }
                if (!doNotAdd) {
                    this.transceivers.push(transceiver);
                }
                return transceiver;
            };

            RTCPeerConnection.prototype.addTrack = function(track, stream) {
                if (this._isClosed) {
                    throw makeError('InvalidStateError',
                        'Attempted to call addTrack on a closed peerconnection.');
                }

                var alreadyExists = this.transceivers.find(function(s) {
                    return s.track === track;
                });

                if (alreadyExists) {
                    throw makeError('InvalidAccessError', 'Track already exists.');
                }

                var transceiver;
                for (var i = 0; i < this.transceivers.length; i++) {
                    if (!this.transceivers[i].track &&
                        this.transceivers[i].kind === track.kind) {
                        transceiver = this.transceivers[i];
                    }
                }
                if (!transceiver) {
                    transceiver = this._createTransceiver(track.kind);
                }

                this._maybeFireNegotiationNeeded();

                if (this.localStreams.indexOf(stream) === -1) {
                    this.localStreams.push(stream);
                }

                transceiver.track = track;
                transceiver.stream = stream;
                transceiver.rtpSender = new window.RTCRtpSender(track,
                    transceiver.dtlsTransport);
                return transceiver.rtpSender;
            };

            RTCPeerConnection.prototype.addStream = function(stream) {
                var pc = this;
                if (edgeVersion >= 15025) {
                    stream.getTracks().forEach(function(track) {
                        pc.addTrack(track, stream);
                    });
                } else {
                    // Clone is necessary for local demos mostly, attaching directly
                    // to two different senders does not work (build 10547).
                    // Fixed in 15025 (or earlier)
                    var clonedStream = stream.clone();
                    stream.getTracks().forEach(function(track, idx) {
                        var clonedTrack = clonedStream.getTracks()[idx];
                        track.addEventListener('enabled', function(event) {
                            clonedTrack.enabled = event.enabled;
                        });
                    });
                    clonedStream.getTracks().forEach(function(track) {
                        pc.addTrack(track, clonedStream);
                    });
                }
            };

            RTCPeerConnection.prototype.removeTrack = function(sender) {
                if (this._isClosed) {
                    throw makeError('InvalidStateError',
                        'Attempted to call removeTrack on a closed peerconnection.');
                }

                if (!(sender instanceof window.RTCRtpSender)) {
                    throw new TypeError('Argument 1 of RTCPeerConnection.removeTrack ' +
                        'does not implement interface RTCRtpSender.');
                }

                var transceiver = this.transceivers.find(function(t) {
                    return t.rtpSender === sender;
                });

                if (!transceiver) {
                    throw makeError('InvalidAccessError',
                        'Sender was not created by this connection.');
                }
                var stream = transceiver.stream;

                transceiver.rtpSender.stop();
                transceiver.rtpSender = null;
                transceiver.track = null;
                transceiver.stream = null;

                // remove the stream from the set of local streams
                var localStreams = this.transceivers.map(function(t) {
                    return t.stream;
                });
                if (localStreams.indexOf(stream) === -1 &&
                    this.localStreams.indexOf(stream) > -1) {
                    this.localStreams.splice(this.localStreams.indexOf(stream), 1);
                }

                this._maybeFireNegotiationNeeded();
            };

            RTCPeerConnection.prototype.removeStream = function(stream) {
                var pc = this;
                stream.getTracks().forEach(function(track) {
                    var sender = pc.getSenders().find(function(s) {
                        return s.track === track;
                    });
                    if (sender) {
                        pc.removeTrack(sender);
                    }
                });
            };

            RTCPeerConnection.prototype.getSenders = function() {
                return this.transceivers.filter(function(transceiver) {
                    return !!transceiver.rtpSender;
                })
                    .map(function(transceiver) {
                        return transceiver.rtpSender;
                    });
            };

            RTCPeerConnection.prototype.getReceivers = function() {
                return this.transceivers.filter(function(transceiver) {
                    return !!transceiver.rtpReceiver;
                })
                    .map(function(transceiver) {
                        return transceiver.rtpReceiver;
                    });
            };


            RTCPeerConnection.prototype._createIceGatherer = function(sdpMLineIndex,
                                                                      usingBundle) {
                var pc = this;
                if (usingBundle && sdpMLineIndex > 0) {
                    return this.transceivers[0].iceGatherer;
                } else if (this._iceGatherers.length) {
                    return this._iceGatherers.shift();
                }
                var iceGatherer = new window.RTCIceGatherer({
                    iceServers: this._config.iceServers,
                    gatherPolicy: this._config.iceTransportPolicy
                });
                Object.defineProperty(iceGatherer, 'state',
                    {value: 'new', writable: true}
                );

                this.transceivers[sdpMLineIndex].bufferedCandidateEvents = [];
                this.transceivers[sdpMLineIndex].bufferCandidates = function(event) {
                    var end = !event.candidate || Object.keys(event.candidate).length === 0;
                    // polyfill since RTCIceGatherer.state is not implemented in
                    // Edge 10547 yet.
                    iceGatherer.state = end ? 'completed' : 'gathering';
                    if (pc.transceivers[sdpMLineIndex].bufferedCandidateEvents !== null) {
                        pc.transceivers[sdpMLineIndex].bufferedCandidateEvents.push(event);
                    }
                };
                iceGatherer.addEventListener('localcandidate',
                    this.transceivers[sdpMLineIndex].bufferCandidates);
                return iceGatherer;
            };

            // start gathering from an RTCIceGatherer.
            RTCPeerConnection.prototype._gather = function(mid, sdpMLineIndex) {
                var pc = this;
                var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
                if (iceGatherer.onlocalcandidate) {
                    return;
                }
                var bufferedCandidateEvents =
                    this.transceivers[sdpMLineIndex].bufferedCandidateEvents;
                this.transceivers[sdpMLineIndex].bufferedCandidateEvents = null;
                iceGatherer.removeEventListener('localcandidate',
                    this.transceivers[sdpMLineIndex].bufferCandidates);
                iceGatherer.onlocalcandidate = function(evt) {
                    if (pc.usingBundle && sdpMLineIndex > 0) {
                        // if we know that we use bundle we can drop candidates with
                        // ѕdpMLineIndex > 0. If we don't do this then our state gets
                        // confused since we dispose the extra ice gatherer.
                        return;
                    }
                    var event = new Event('icecandidate');
                    event.candidate = {sdpMid: mid, sdpMLineIndex: sdpMLineIndex};

                    var cand = evt.candidate;
                    // Edge emits an empty object for RTCIceCandidateComplete‥
                    var end = !cand || Object.keys(cand).length === 0;
                    if (end) {
                        // polyfill since RTCIceGatherer.state is not implemented in
                        // Edge 10547 yet.
                        if (iceGatherer.state === 'new' || iceGatherer.state === 'gathering') {
                            iceGatherer.state = 'completed';
                        }
                    } else {
                        if (iceGatherer.state === 'new') {
                            iceGatherer.state = 'gathering';
                        }
                        // RTCIceCandidate doesn't have a component, needs to be added
                        cand.component = 1;
                        // also the usernameFragment. TODO: update SDP to take both variants.
                        cand.ufrag = iceGatherer.getLocalParameters().usernameFragment;

                        var serializedCandidate = SDPUtils.writeCandidate(cand);
                        event.candidate = Object.assign(event.candidate,
                            SDPUtils.parseCandidate(serializedCandidate));

                        event.candidate.candidate = serializedCandidate;
                        event.candidate.toJSON = function() {
                            return {
                                candidate: event.candidate.candidate,
                                sdpMid: event.candidate.sdpMid,
                                sdpMLineIndex: event.candidate.sdpMLineIndex,
                                usernameFragment: event.candidate.usernameFragment
                            };
                        };
                    }

                    // update local description.
                    var sections = SDPUtils.getMediaSections(pc._localDescription.sdp);
                    if (!end) {
                        sections[event.candidate.sdpMLineIndex] +=
                            'a=' + event.candidate.candidate + '\r\n';
                    } else {
                        sections[event.candidate.sdpMLineIndex] +=
                            'a=end-of-candidates\r\n';
                    }
                    pc._localDescription.sdp =
                        SDPUtils.getDescription(pc._localDescription.sdp) +
                        sections.join('');
                    var complete = pc.transceivers.every(function(transceiver) {
                        return transceiver.iceGatherer &&
                            transceiver.iceGatherer.state === 'completed';
                    });

                    if (pc.iceGatheringState !== 'gathering') {
                        pc.iceGatheringState = 'gathering';
                        pc._emitGatheringStateChange();
                    }

                    // Emit candidate. Also emit null candidate when all gatherers are
                    // complete.
                    if (!end) {
                        pc._dispatchEvent('icecandidate', event);
                    }
                    if (complete) {
                        pc._dispatchEvent('icecandidate', new Event('icecandidate'));
                        pc.iceGatheringState = 'complete';
                        pc._emitGatheringStateChange();
                    }
                };

                // emit already gathered candidates.
                window.setTimeout(function() {
                    bufferedCandidateEvents.forEach(function(e) {
                        iceGatherer.onlocalcandidate(e);
                    });
                }, 0);
            };

            // Create ICE transport and DTLS transport.
            RTCPeerConnection.prototype._createIceAndDtlsTransports = function() {
                var pc = this;
                var iceTransport = new window.RTCIceTransport(null);
                iceTransport.onicestatechange = function() {
                    pc._updateIceConnectionState();
                    pc._updateConnectionState();
                };

                var dtlsTransport = new window.RTCDtlsTransport(iceTransport);
                dtlsTransport.ondtlsstatechange = function() {
                    pc._updateConnectionState();
                };
                dtlsTransport.onerror = function() {
                    // onerror does not set state to failed by itself.
                    Object.defineProperty(dtlsTransport, 'state',
                        {value: 'failed', writable: true});
                    pc._updateConnectionState();
                };

                return {
                    iceTransport: iceTransport,
                    dtlsTransport: dtlsTransport
                };
            };

            // Destroy ICE gatherer, ICE transport and DTLS transport.
            // Without triggering the callbacks.
            RTCPeerConnection.prototype._disposeIceAndDtlsTransports = function(
                sdpMLineIndex) {
                var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
                if (iceGatherer) {
                    delete iceGatherer.onlocalcandidate;
                    delete this.transceivers[sdpMLineIndex].iceGatherer;
                }
                var iceTransport = this.transceivers[sdpMLineIndex].iceTransport;
                if (iceTransport) {
                    delete iceTransport.onicestatechange;
                    delete this.transceivers[sdpMLineIndex].iceTransport;
                }
                var dtlsTransport = this.transceivers[sdpMLineIndex].dtlsTransport;
                if (dtlsTransport) {
                    delete dtlsTransport.ondtlsstatechange;
                    delete dtlsTransport.onerror;
                    delete this.transceivers[sdpMLineIndex].dtlsTransport;
                }
            };

            // Start the RTP Sender and Receiver for a transceiver.
            RTCPeerConnection.prototype._transceive = function(transceiver,
                                                               send, recv) {
                var params = getCommonCapabilities(transceiver.localCapabilities,
                    transceiver.remoteCapabilities);
                if (send && transceiver.rtpSender) {
                    params.encodings = transceiver.sendEncodingParameters;
                    params.rtcp = {
                        cname: SDPUtils.localCName,
                        compound: transceiver.rtcpParameters.compound
                    };
                    if (transceiver.recvEncodingParameters.length) {
                        params.rtcp.ssrc = transceiver.recvEncodingParameters[0].ssrc;
                    }
                    transceiver.rtpSender.send(params);
                }
                if (recv && transceiver.rtpReceiver && params.codecs.length > 0) {
                    // remove RTX field in Edge 14942
                    if (transceiver.kind === 'video'
                        && transceiver.recvEncodingParameters
                        && edgeVersion < 15019) {
                        transceiver.recvEncodingParameters.forEach(function(p) {
                            delete p.rtx;
                        });
                    }
                    if (transceiver.recvEncodingParameters.length) {
                        params.encodings = transceiver.recvEncodingParameters;
                    } else {
                        params.encodings = [{}];
                    }
                    params.rtcp = {
                        compound: transceiver.rtcpParameters.compound
                    };
                    if (transceiver.rtcpParameters.cname) {
                        params.rtcp.cname = transceiver.rtcpParameters.cname;
                    }
                    if (transceiver.sendEncodingParameters.length) {
                        params.rtcp.ssrc = transceiver.sendEncodingParameters[0].ssrc;
                    }
                    transceiver.rtpReceiver.receive(params);
                }
            };

            RTCPeerConnection.prototype.setLocalDescription = function(description) {
                var pc = this;

                // Note: pranswer is not supported.
                if (['offer', 'answer'].indexOf(description.type) === -1) {
                    return Promise.reject(makeError('TypeError',
                        'Unsupported type "' + description.type + '"'));
                }

                if (!isActionAllowedInSignalingState('setLocalDescription',
                    description.type, pc.signalingState) || pc._isClosed) {
                    return Promise.reject(makeError('InvalidStateError',
                        'Can not set local ' + description.type +
                        ' in state ' + pc.signalingState));
                }

                var sections;
                var sessionpart;
                if (description.type === 'offer') {
                    // VERY limited support for SDP munging. Limited to:
                    // * changing the order of codecs
                    sections = SDPUtils.splitSections(description.sdp);
                    sessionpart = sections.shift();
                    sections.forEach(function(mediaSection, sdpMLineIndex) {
                        var caps = SDPUtils.parseRtpParameters(mediaSection);
                        pc.transceivers[sdpMLineIndex].localCapabilities = caps;
                    });

                    pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                        pc._gather(transceiver.mid, sdpMLineIndex);
                    });
                } else if (description.type === 'answer') {
                    sections = SDPUtils.splitSections(pc._remoteDescription.sdp);
                    sessionpart = sections.shift();
                    var isIceLite = SDPUtils.matchPrefix(sessionpart,
                        'a=ice-lite').length > 0;
                    sections.forEach(function(mediaSection, sdpMLineIndex) {
                        var transceiver = pc.transceivers[sdpMLineIndex];
                        var iceGatherer = transceiver.iceGatherer;
                        var iceTransport = transceiver.iceTransport;
                        var dtlsTransport = transceiver.dtlsTransport;
                        var localCapabilities = transceiver.localCapabilities;
                        var remoteCapabilities = transceiver.remoteCapabilities;

                        // treat bundle-only as not-rejected.
                        var rejected = SDPUtils.isRejected(mediaSection) &&
                            SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0;

                        if (!rejected && !transceiver.rejected) {
                            var remoteIceParameters = SDPUtils.getIceParameters(
                                mediaSection, sessionpart);
                            var remoteDtlsParameters = SDPUtils.getDtlsParameters(
                                mediaSection, sessionpart);
                            if (isIceLite) {
                                remoteDtlsParameters.role = 'server';
                            }

                            if (!pc.usingBundle || sdpMLineIndex === 0) {
                                pc._gather(transceiver.mid, sdpMLineIndex);
                                if (iceTransport.state === 'new') {
                                    iceTransport.start(iceGatherer, remoteIceParameters,
                                        isIceLite ? 'controlling' : 'controlled');
                                }
                                if (dtlsTransport.state === 'new') {
                                    dtlsTransport.start(remoteDtlsParameters);
                                }
                            }

                            // Calculate intersection of capabilities.
                            var params = getCommonCapabilities(localCapabilities,
                                remoteCapabilities);

                            // Start the RTCRtpSender. The RTCRtpReceiver for this
                            // transceiver has already been started in setRemoteDescription.
                            pc._transceive(transceiver,
                                params.codecs.length > 0,
                                false);
                        }
                    });
                }

                pc._localDescription = {
                    type: description.type,
                    sdp: description.sdp
                };
                if (description.type === 'offer') {
                    pc._updateSignalingState('have-local-offer');
                } else {
                    pc._updateSignalingState('stable');
                }

                return Promise.resolve();
            };

            RTCPeerConnection.prototype.setRemoteDescription = function(description) {
                var pc = this;

                // Note: pranswer is not supported.
                if (['offer', 'answer'].indexOf(description.type) === -1) {
                    return Promise.reject(makeError('TypeError',
                        'Unsupported type "' + description.type + '"'));
                }

                if (!isActionAllowedInSignalingState('setRemoteDescription',
                    description.type, pc.signalingState) || pc._isClosed) {
                    return Promise.reject(makeError('InvalidStateError',
                        'Can not set remote ' + description.type +
                        ' in state ' + pc.signalingState));
                }

                var streams = {};
                pc.remoteStreams.forEach(function(stream) {
                    streams[stream.id] = stream;
                });
                var receiverList = [];
                var sections = SDPUtils.splitSections(description.sdp);
                var sessionpart = sections.shift();
                var isIceLite = SDPUtils.matchPrefix(sessionpart,
                    'a=ice-lite').length > 0;
                var usingBundle = SDPUtils.matchPrefix(sessionpart,
                    'a=group:BUNDLE ').length > 0;
                pc.usingBundle = usingBundle;
                var iceOptions = SDPUtils.matchPrefix(sessionpart,
                    'a=ice-options:')[0];
                if (iceOptions) {
                    pc.canTrickleIceCandidates = iceOptions.substr(14).split(' ')
                        .indexOf('trickle') >= 0;
                } else {
                    pc.canTrickleIceCandidates = false;
                }

                sections.forEach(function(mediaSection, sdpMLineIndex) {
                    var lines = SDPUtils.splitLines(mediaSection);
                    var kind = SDPUtils.getKind(mediaSection);
                    // treat bundle-only as not-rejected.
                    var rejected = SDPUtils.isRejected(mediaSection) &&
                        SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0;
                    var protocol = lines[0].substr(2).split(' ')[2];

                    var direction = SDPUtils.getDirection(mediaSection, sessionpart);
                    var remoteMsid = SDPUtils.parseMsid(mediaSection);

                    var mid = SDPUtils.getMid(mediaSection) || SDPUtils.generateIdentifier();

                    // Reject datachannels which are not implemented yet.
                    if (rejected || (kind === 'application' && (protocol === 'DTLS/SCTP' ||
                        protocol === 'UDP/DTLS/SCTP'))) {
                        // TODO: this is dangerous in the case where a non-rejected m-line
                        //     becomes rejected.
                        pc.transceivers[sdpMLineIndex] = {
                            mid: mid,
                            kind: kind,
                            protocol: protocol,
                            rejected: true
                        };
                        return;
                    }

                    if (!rejected && pc.transceivers[sdpMLineIndex] &&
                        pc.transceivers[sdpMLineIndex].rejected) {
                        // recycle a rejected transceiver.
                        pc.transceivers[sdpMLineIndex] = pc._createTransceiver(kind, true);
                    }

                    var transceiver;
                    var iceGatherer;
                    var iceTransport;
                    var dtlsTransport;
                    var rtpReceiver;
                    var sendEncodingParameters;
                    var recvEncodingParameters;
                    var localCapabilities;

                    var track;
                    // FIXME: ensure the mediaSection has rtcp-mux set.
                    var remoteCapabilities = SDPUtils.parseRtpParameters(mediaSection);
                    var remoteIceParameters;
                    var remoteDtlsParameters;
                    if (!rejected) {
                        remoteIceParameters = SDPUtils.getIceParameters(mediaSection,
                            sessionpart);
                        remoteDtlsParameters = SDPUtils.getDtlsParameters(mediaSection,
                            sessionpart);
                        remoteDtlsParameters.role = 'client';
                    }
                    recvEncodingParameters =
                        SDPUtils.parseRtpEncodingParameters(mediaSection);

                    var rtcpParameters = SDPUtils.parseRtcpParameters(mediaSection);

                    var isComplete = SDPUtils.matchPrefix(mediaSection,
                        'a=end-of-candidates', sessionpart).length > 0;
                    var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
                        .map(function(cand) {
                            return SDPUtils.parseCandidate(cand);
                        })
                        .filter(function(cand) {
                            return cand.component === 1;
                        });

                    // Check if we can use BUNDLE and dispose transports.
                    if ((description.type === 'offer' || description.type === 'answer') &&
                        !rejected && usingBundle && sdpMLineIndex > 0 &&
                        pc.transceivers[sdpMLineIndex]) {
                        pc._disposeIceAndDtlsTransports(sdpMLineIndex);
                        pc.transceivers[sdpMLineIndex].iceGatherer =
                            pc.transceivers[0].iceGatherer;
                        pc.transceivers[sdpMLineIndex].iceTransport =
                            pc.transceivers[0].iceTransport;
                        pc.transceivers[sdpMLineIndex].dtlsTransport =
                            pc.transceivers[0].dtlsTransport;
                        if (pc.transceivers[sdpMLineIndex].rtpSender) {
                            pc.transceivers[sdpMLineIndex].rtpSender.setTransport(
                                pc.transceivers[0].dtlsTransport);
                        }
                        if (pc.transceivers[sdpMLineIndex].rtpReceiver) {
                            pc.transceivers[sdpMLineIndex].rtpReceiver.setTransport(
                                pc.transceivers[0].dtlsTransport);
                        }
                    }
                    if (description.type === 'offer' && !rejected) {
                        transceiver = pc.transceivers[sdpMLineIndex] ||
                            pc._createTransceiver(kind);
                        transceiver.mid = mid;

                        if (!transceiver.iceGatherer) {
                            transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
                                usingBundle);
                        }

                        if (cands.length && transceiver.iceTransport.state === 'new') {
                            if (isComplete && (!usingBundle || sdpMLineIndex === 0)) {
                                transceiver.iceTransport.setRemoteCandidates(cands);
                            } else {
                                cands.forEach(function(candidate) {
                                    maybeAddCandidate(transceiver.iceTransport, candidate);
                                });
                            }
                        }

                        localCapabilities = window.RTCRtpReceiver.getCapabilities(kind);

                        // filter RTX until additional stuff needed for RTX is implemented
                        // in adapter.js
                        if (edgeVersion < 15019) {
                            localCapabilities.codecs = localCapabilities.codecs.filter(
                                function(codec) {
                                    return codec.name !== 'rtx';
                                });
                        }

                        sendEncodingParameters = transceiver.sendEncodingParameters || [{
                            ssrc: (2 * sdpMLineIndex + 2) * 1001
                        }];

                        // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
                        var isNewTrack = false;
                        if (direction === 'sendrecv' || direction === 'sendonly') {
                            isNewTrack = !transceiver.rtpReceiver;
                            rtpReceiver = transceiver.rtpReceiver ||
                                new window.RTCRtpReceiver(transceiver.dtlsTransport, kind);

                            if (isNewTrack) {
                                var stream;
                                track = rtpReceiver.track;
                                // FIXME: does not work with Plan B.
                                if (remoteMsid && remoteMsid.stream === '-') {
                                    // no-op. a stream id of '-' means: no associated stream.
                                } else if (remoteMsid) {
                                    if (!streams[remoteMsid.stream]) {
                                        streams[remoteMsid.stream] = new window.MediaStream();
                                        Object.defineProperty(streams[remoteMsid.stream], 'id', {
                                            get: function() {
                                                return remoteMsid.stream;
                                            }
                                        });
                                    }
                                    Object.defineProperty(track, 'id', {
                                        get: function() {
                                            return remoteMsid.track;
                                        }
                                    });
                                    stream = streams[remoteMsid.stream];
                                } else {
                                    if (!streams.default) {
                                        streams.default = new window.MediaStream();
                                    }
                                    stream = streams.default;
                                }
                                if (stream) {
                                    addTrackToStreamAndFireEvent(track, stream);
                                    transceiver.associatedRemoteMediaStreams.push(stream);
                                }
                                receiverList.push([track, rtpReceiver, stream]);
                            }
                        } else if (transceiver.rtpReceiver && transceiver.rtpReceiver.track) {
                            transceiver.associatedRemoteMediaStreams.forEach(function(s) {
                                var nativeTrack = s.getTracks().find(function(t) {
                                    return t.id === transceiver.rtpReceiver.track.id;
                                });
                                if (nativeTrack) {
                                    removeTrackFromStreamAndFireEvent(nativeTrack, s);
                                }
                            });
                            transceiver.associatedRemoteMediaStreams = [];
                        }

                        transceiver.localCapabilities = localCapabilities;
                        transceiver.remoteCapabilities = remoteCapabilities;
                        transceiver.rtpReceiver = rtpReceiver;
                        transceiver.rtcpParameters = rtcpParameters;
                        transceiver.sendEncodingParameters = sendEncodingParameters;
                        transceiver.recvEncodingParameters = recvEncodingParameters;

                        // Start the RTCRtpReceiver now. The RTPSender is started in
                        // setLocalDescription.
                        pc._transceive(pc.transceivers[sdpMLineIndex],
                            false,
                            isNewTrack);
                    } else if (description.type === 'answer' && !rejected) {
                        transceiver = pc.transceivers[sdpMLineIndex];
                        iceGatherer = transceiver.iceGatherer;
                        iceTransport = transceiver.iceTransport;
                        dtlsTransport = transceiver.dtlsTransport;
                        rtpReceiver = transceiver.rtpReceiver;
                        sendEncodingParameters = transceiver.sendEncodingParameters;
                        localCapabilities = transceiver.localCapabilities;

                        pc.transceivers[sdpMLineIndex].recvEncodingParameters =
                            recvEncodingParameters;
                        pc.transceivers[sdpMLineIndex].remoteCapabilities =
                            remoteCapabilities;
                        pc.transceivers[sdpMLineIndex].rtcpParameters = rtcpParameters;

                        if (cands.length && iceTransport.state === 'new') {
                            if ((isIceLite || isComplete) &&
                                (!usingBundle || sdpMLineIndex === 0)) {
                                iceTransport.setRemoteCandidates(cands);
                            } else {
                                cands.forEach(function(candidate) {
                                    maybeAddCandidate(transceiver.iceTransport, candidate);
                                });
                            }
                        }

                        if (!usingBundle || sdpMLineIndex === 0) {
                            if (iceTransport.state === 'new') {
                                iceTransport.start(iceGatherer, remoteIceParameters,
                                    'controlling');
                            }
                            if (dtlsTransport.state === 'new') {
                                dtlsTransport.start(remoteDtlsParameters);
                            }
                        }

                        // If the offer contained RTX but the answer did not,
                        // remove RTX from sendEncodingParameters.
                        var commonCapabilities = getCommonCapabilities(
                            transceiver.localCapabilities,
                            transceiver.remoteCapabilities);

                        var hasRtx = commonCapabilities.codecs.filter(function(c) {
                            return c.name.toLowerCase() === 'rtx';
                        }).length;
                        if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
                            delete transceiver.sendEncodingParameters[0].rtx;
                        }

                        pc._transceive(transceiver,
                            direction === 'sendrecv' || direction === 'recvonly',
                            direction === 'sendrecv' || direction === 'sendonly');

                        // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
                        if (rtpReceiver &&
                            (direction === 'sendrecv' || direction === 'sendonly')) {
                            track = rtpReceiver.track;
                            if (remoteMsid) {
                                if (!streams[remoteMsid.stream]) {
                                    streams[remoteMsid.stream] = new window.MediaStream();
                                }
                                addTrackToStreamAndFireEvent(track, streams[remoteMsid.stream]);
                                receiverList.push([track, rtpReceiver, streams[remoteMsid.stream]]);
                            } else {
                                if (!streams.default) {
                                    streams.default = new window.MediaStream();
                                }
                                addTrackToStreamAndFireEvent(track, streams.default);
                                receiverList.push([track, rtpReceiver, streams.default]);
                            }
                        } else {
                            // FIXME: actually the receiver should be created later.
                            delete transceiver.rtpReceiver;
                        }
                    }
                });

                if (pc._dtlsRole === undefined) {
                    pc._dtlsRole = description.type === 'offer' ? 'active' : 'passive';
                }

                pc._remoteDescription = {
                    type: description.type,
                    sdp: description.sdp
                };
                if (description.type === 'offer') {
                    pc._updateSignalingState('have-remote-offer');
                } else {
                    pc._updateSignalingState('stable');
                }
                Object.keys(streams).forEach(function(sid) {
                    var stream = streams[sid];
                    if (stream.getTracks().length) {
                        if (pc.remoteStreams.indexOf(stream) === -1) {
                            pc.remoteStreams.push(stream);
                            var event = new Event('addstream');
                            event.stream = stream;
                            window.setTimeout(function() {
                                pc._dispatchEvent('addstream', event);
                            });
                        }

                        receiverList.forEach(function(item) {
                            var track = item[0];
                            var receiver = item[1];
                            if (stream.id !== item[2].id) {
                                return;
                            }
                            fireAddTrack(pc, track, receiver, [stream]);
                        });
                    }
                });
                receiverList.forEach(function(item) {
                    if (item[2]) {
                        return;
                    }
                    fireAddTrack(pc, item[0], item[1], []);
                });

                // check whether addIceCandidate({}) was called within four seconds after
                // setRemoteDescription.
                window.setTimeout(function() {
                    if (!(pc && pc.transceivers)) {
                        return;
                    }
                    pc.transceivers.forEach(function(transceiver) {
                        if (transceiver.iceTransport &&
                            transceiver.iceTransport.state === 'new' &&
                            transceiver.iceTransport.getRemoteCandidates().length > 0) {
                            console.warn('Timeout for addRemoteCandidate. Consider sending ' +
                                'an end-of-candidates notification');
                            transceiver.iceTransport.addRemoteCandidate({});
                        }
                    });
                }, 4000);

                return Promise.resolve();
            };

            RTCPeerConnection.prototype.close = function() {
                this.transceivers.forEach(function(transceiver) {
                    /* not yet
      if (transceiver.iceGatherer) {
        transceiver.iceGatherer.close();
      }
      */
                    if (transceiver.iceTransport) {
                        transceiver.iceTransport.stop();
                    }
                    if (transceiver.dtlsTransport) {
                        transceiver.dtlsTransport.stop();
                    }
                    if (transceiver.rtpSender) {
                        transceiver.rtpSender.stop();
                    }
                    if (transceiver.rtpReceiver) {
                        transceiver.rtpReceiver.stop();
                    }
                });
                // FIXME: clean up tracks, local streams, remote streams, etc
                this._isClosed = true;
                this._updateSignalingState('closed');
            };

            // Update the signaling state.
            RTCPeerConnection.prototype._updateSignalingState = function(newState) {
                this.signalingState = newState;
                var event = new Event('signalingstatechange');
                this._dispatchEvent('signalingstatechange', event);
            };

            // Determine whether to fire the negotiationneeded event.
            RTCPeerConnection.prototype._maybeFireNegotiationNeeded = function() {
                var pc = this;
                if (this.signalingState !== 'stable' || this.needNegotiation === true) {
                    return;
                }
                this.needNegotiation = true;
                window.setTimeout(function() {
                    if (pc.needNegotiation) {
                        pc.needNegotiation = false;
                        var event = new Event('negotiationneeded');
                        pc._dispatchEvent('negotiationneeded', event);
                    }
                }, 0);
            };

            // Update the ice connection state.
            RTCPeerConnection.prototype._updateIceConnectionState = function() {
                var newState;
                var states = {
                    'new': 0,
                    closed: 0,
                    checking: 0,
                    connected: 0,
                    completed: 0,
                    disconnected: 0,
                    failed: 0
                };
                this.transceivers.forEach(function(transceiver) {
                    if (transceiver.iceTransport && !transceiver.rejected) {
                        states[transceiver.iceTransport.state]++;
                    }
                });

                newState = 'new';
                if (states.failed > 0) {
                    newState = 'failed';
                } else if (states.checking > 0) {
                    newState = 'checking';
                } else if (states.disconnected > 0) {
                    newState = 'disconnected';
                } else if (states.new > 0) {
                    newState = 'new';
                } else if (states.connected > 0) {
                    newState = 'connected';
                } else if (states.completed > 0) {
                    newState = 'completed';
                }

                if (newState !== this.iceConnectionState) {
                    this.iceConnectionState = newState;
                    var event = new Event('iceconnectionstatechange');
                    this._dispatchEvent('iceconnectionstatechange', event);
                }
            };

            // Update the connection state.
            RTCPeerConnection.prototype._updateConnectionState = function() {
                var newState;
                var states = {
                    'new': 0,
                    closed: 0,
                    connecting: 0,
                    connected: 0,
                    completed: 0,
                    disconnected: 0,
                    failed: 0
                };
                this.transceivers.forEach(function(transceiver) {
                    if (transceiver.iceTransport && transceiver.dtlsTransport &&
                        !transceiver.rejected) {
                        states[transceiver.iceTransport.state]++;
                        states[transceiver.dtlsTransport.state]++;
                    }
                });
                // ICETransport.completed and connected are the same for this purpose.
                states.connected += states.completed;

                newState = 'new';
                if (states.failed > 0) {
                    newState = 'failed';
                } else if (states.connecting > 0) {
                    newState = 'connecting';
                } else if (states.disconnected > 0) {
                    newState = 'disconnected';
                } else if (states.new > 0) {
                    newState = 'new';
                } else if (states.connected > 0) {
                    newState = 'connected';
                }

                if (newState !== this.connectionState) {
                    this.connectionState = newState;
                    var event = new Event('connectionstatechange');
                    this._dispatchEvent('connectionstatechange', event);
                }
            };

            RTCPeerConnection.prototype.createOffer = function() {
                var pc = this;

                if (pc._isClosed) {
                    return Promise.reject(makeError('InvalidStateError',
                        'Can not call createOffer after close'));
                }

                var numAudioTracks = pc.transceivers.filter(function(t) {
                    return t.kind === 'audio';
                }).length;
                var numVideoTracks = pc.transceivers.filter(function(t) {
                    return t.kind === 'video';
                }).length;

                // Determine number of audio and video tracks we need to send/recv.
                var offerOptions = arguments[0];
                if (offerOptions) {
                    // Reject Chrome legacy constraints.
                    if (offerOptions.mandatory || offerOptions.optional) {
                        throw new TypeError(
                            'Legacy mandatory/optional constraints not supported.');
                    }
                    if (offerOptions.offerToReceiveAudio !== undefined) {
                        if (offerOptions.offerToReceiveAudio === true) {
                            numAudioTracks = 1;
                        } else if (offerOptions.offerToReceiveAudio === false) {
                            numAudioTracks = 0;
                        } else {
                            numAudioTracks = offerOptions.offerToReceiveAudio;
                        }
                    }
                    if (offerOptions.offerToReceiveVideo !== undefined) {
                        if (offerOptions.offerToReceiveVideo === true) {
                            numVideoTracks = 1;
                        } else if (offerOptions.offerToReceiveVideo === false) {
                            numVideoTracks = 0;
                        } else {
                            numVideoTracks = offerOptions.offerToReceiveVideo;
                        }
                    }
                }

                pc.transceivers.forEach(function(transceiver) {
                    if (transceiver.kind === 'audio') {
                        numAudioTracks--;
                        if (numAudioTracks < 0) {
                            transceiver.wantReceive = false;
                        }
                    } else if (transceiver.kind === 'video') {
                        numVideoTracks--;
                        if (numVideoTracks < 0) {
                            transceiver.wantReceive = false;
                        }
                    }
                });

                // Create M-lines for recvonly streams.
                while (numAudioTracks > 0 || numVideoTracks > 0) {
                    if (numAudioTracks > 0) {
                        pc._createTransceiver('audio');
                        numAudioTracks--;
                    }
                    if (numVideoTracks > 0) {
                        pc._createTransceiver('video');
                        numVideoTracks--;
                    }
                }

                var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
                    pc._sdpSessionVersion++);
                pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                    // For each track, create an ice gatherer, ice transport,
                    // dtls transport, potentially rtpsender and rtpreceiver.
                    var track = transceiver.track;
                    var kind = transceiver.kind;
                    var mid = transceiver.mid || SDPUtils.generateIdentifier();
                    transceiver.mid = mid;

                    if (!transceiver.iceGatherer) {
                        transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
                            pc.usingBundle);
                    }

                    var localCapabilities = window.RTCRtpSender.getCapabilities(kind);
                    // filter RTX until additional stuff needed for RTX is implemented
                    // in adapter.js
                    if (edgeVersion < 15019) {
                        localCapabilities.codecs = localCapabilities.codecs.filter(
                            function(codec) {
                                return codec.name !== 'rtx';
                            });
                    }
                    localCapabilities.codecs.forEach(function(codec) {
                        // work around https://bugs.chromium.org/p/webrtc/issues/detail?id=6552
                        // by adding level-asymmetry-allowed=1
                        if (codec.name === 'H264' &&
                            codec.parameters['level-asymmetry-allowed'] === undefined) {
                            codec.parameters['level-asymmetry-allowed'] = '1';
                        }

                        // for subsequent offers, we might have to re-use the payload
                        // type of the last offer.
                        if (transceiver.remoteCapabilities &&
                            transceiver.remoteCapabilities.codecs) {
                            transceiver.remoteCapabilities.codecs.forEach(function(remoteCodec) {
                                if (codec.name.toLowerCase() === remoteCodec.name.toLowerCase() &&
                                    codec.clockRate === remoteCodec.clockRate) {
                                    codec.preferredPayloadType = remoteCodec.payloadType;
                                }
                            });
                        }
                    });
                    localCapabilities.headerExtensions.forEach(function(hdrExt) {
                        var remoteExtensions = transceiver.remoteCapabilities &&
                            transceiver.remoteCapabilities.headerExtensions || [];
                        remoteExtensions.forEach(function(rHdrExt) {
                            if (hdrExt.uri === rHdrExt.uri) {
                                hdrExt.id = rHdrExt.id;
                            }
                        });
                    });

                    // generate an ssrc now, to be used later in rtpSender.send
                    var sendEncodingParameters = transceiver.sendEncodingParameters || [{
                        ssrc: (2 * sdpMLineIndex + 1) * 1001
                    }];
                    if (track) {
                        // add RTX
                        if (edgeVersion >= 15019 && kind === 'video' &&
                            !sendEncodingParameters[0].rtx) {
                            sendEncodingParameters[0].rtx = {
                                ssrc: sendEncodingParameters[0].ssrc + 1
                            };
                        }
                    }

                    if (transceiver.wantReceive) {
                        transceiver.rtpReceiver = new window.RTCRtpReceiver(
                            transceiver.dtlsTransport, kind);
                    }

                    transceiver.localCapabilities = localCapabilities;
                    transceiver.sendEncodingParameters = sendEncodingParameters;
                });

                // always offer BUNDLE and dispose on return if not supported.
                if (pc._config.bundlePolicy !== 'max-compat') {
                    sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
                        return t.mid;
                    }).join(' ') + '\r\n';
                }
                sdp += 'a=ice-options:trickle\r\n';

                pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                    sdp += writeMediaSection(transceiver, transceiver.localCapabilities,
                        'offer', transceiver.stream, pc._dtlsRole);
                    sdp += 'a=rtcp-rsize\r\n';

                    if (transceiver.iceGatherer && pc.iceGatheringState !== 'new' &&
                        (sdpMLineIndex === 0 || !pc.usingBundle)) {
                        transceiver.iceGatherer.getLocalCandidates().forEach(function(cand) {
                            cand.component = 1;
                            sdp += 'a=' + SDPUtils.writeCandidate(cand) + '\r\n';
                        });

                        if (transceiver.iceGatherer.state === 'completed') {
                            sdp += 'a=end-of-candidates\r\n';
                        }
                    }
                });

                var desc = new window.RTCSessionDescription({
                    type: 'offer',
                    sdp: sdp
                });
                return Promise.resolve(desc);
            };

            RTCPeerConnection.prototype.createAnswer = function() {
                var pc = this;

                if (pc._isClosed) {
                    return Promise.reject(makeError('InvalidStateError',
                        'Can not call createAnswer after close'));
                }

                if (!(pc.signalingState === 'have-remote-offer' ||
                    pc.signalingState === 'have-local-pranswer')) {
                    return Promise.reject(makeError('InvalidStateError',
                        'Can not call createAnswer in signalingState ' + pc.signalingState));
                }

                var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
                    pc._sdpSessionVersion++);
                if (pc.usingBundle) {
                    sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
                        return t.mid;
                    }).join(' ') + '\r\n';
                }
                sdp += 'a=ice-options:trickle\r\n';

                var mediaSectionsInOffer = SDPUtils.getMediaSections(
                    pc._remoteDescription.sdp).length;
                pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                    if (sdpMLineIndex + 1 > mediaSectionsInOffer) {
                        return;
                    }
                    if (transceiver.rejected) {
                        if (transceiver.kind === 'application') {
                            if (transceiver.protocol === 'DTLS/SCTP') { // legacy fmt
                                sdp += 'm=application 0 DTLS/SCTP 5000\r\n';
                            } else {
                                sdp += 'm=application 0 ' + transceiver.protocol +
                                    ' webrtc-datachannel\r\n';
                            }
                        } else if (transceiver.kind === 'audio') {
                            sdp += 'm=audio 0 UDP/TLS/RTP/SAVPF 0\r\n' +
                                'a=rtpmap:0 PCMU/8000\r\n';
                        } else if (transceiver.kind === 'video') {
                            sdp += 'm=video 0 UDP/TLS/RTP/SAVPF 120\r\n' +
                                'a=rtpmap:120 VP8/90000\r\n';
                        }
                        sdp += 'c=IN IP4 0.0.0.0\r\n' +
                            'a=inactive\r\n' +
                            'a=mid:' + transceiver.mid + '\r\n';
                        return;
                    }

                    // FIXME: look at direction.
                    if (transceiver.stream) {
                        var localTrack;
                        if (transceiver.kind === 'audio') {
                            localTrack = transceiver.stream.getAudioTracks()[0];
                        } else if (transceiver.kind === 'video') {
                            localTrack = transceiver.stream.getVideoTracks()[0];
                        }
                        if (localTrack) {
                            // add RTX
                            if (edgeVersion >= 15019 && transceiver.kind === 'video' &&
                                !transceiver.sendEncodingParameters[0].rtx) {
                                transceiver.sendEncodingParameters[0].rtx = {
                                    ssrc: transceiver.sendEncodingParameters[0].ssrc + 1
                                };
                            }
                        }
                    }

                    // Calculate intersection of capabilities.
                    var commonCapabilities = getCommonCapabilities(
                        transceiver.localCapabilities,
                        transceiver.remoteCapabilities);

                    var hasRtx = commonCapabilities.codecs.filter(function(c) {
                        return c.name.toLowerCase() === 'rtx';
                    }).length;
                    if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
                        delete transceiver.sendEncodingParameters[0].rtx;
                    }

                    sdp += writeMediaSection(transceiver, commonCapabilities,
                        'answer', transceiver.stream, pc._dtlsRole);
                    if (transceiver.rtcpParameters &&
                        transceiver.rtcpParameters.reducedSize) {
                        sdp += 'a=rtcp-rsize\r\n';
                    }
                });

                var desc = new window.RTCSessionDescription({
                    type: 'answer',
                    sdp: sdp
                });
                return Promise.resolve(desc);
            };

            RTCPeerConnection.prototype.addIceCandidate = function(candidate) {
                var pc = this;
                var sections;
                if (candidate && !(candidate.sdpMLineIndex !== undefined ||
                    candidate.sdpMid)) {
                    return Promise.reject(new TypeError('sdpMLineIndex or sdpMid required'));
                }

                // TODO: needs to go into ops queue.
                return new Promise(function(resolve, reject) {
                    if (!pc._remoteDescription) {
                        return reject(makeError('InvalidStateError',
                            'Can not add ICE candidate without a remote description'));
                    } else if (!candidate || candidate.candidate === '') {
                        for (var j = 0; j < pc.transceivers.length; j++) {
                            if (pc.transceivers[j].rejected) {
                                continue;
                            }
                            pc.transceivers[j].iceTransport.addRemoteCandidate({});
                            sections = SDPUtils.getMediaSections(pc._remoteDescription.sdp);
                            sections[j] += 'a=end-of-candidates\r\n';
                            pc._remoteDescription.sdp =
                                SDPUtils.getDescription(pc._remoteDescription.sdp) +
                                sections.join('');
                            if (pc.usingBundle) {
                                break;
                            }
                        }
                    } else {
                        var sdpMLineIndex = candidate.sdpMLineIndex;
                        if (candidate.sdpMid) {
                            for (var i = 0; i < pc.transceivers.length; i++) {
                                if (pc.transceivers[i].mid === candidate.sdpMid) {
                                    sdpMLineIndex = i;
                                    break;
                                }
                            }
                        }
                        var transceiver = pc.transceivers[sdpMLineIndex];
                        if (transceiver) {
                            if (transceiver.rejected) {
                                return resolve();
                            }
                            var cand = Object.keys(candidate.candidate).length > 0 ?
                                SDPUtils.parseCandidate(candidate.candidate) : {};
                            // Ignore Chrome's invalid candidates since Edge does not like them.
                            if (cand.protocol === 'tcp' && (cand.port === 0 || cand.port === 9)) {
                                return resolve();
                            }
                            // Ignore RTCP candidates, we assume RTCP-MUX.
                            if (cand.component && cand.component !== 1) {
                                return resolve();
                            }
                            // when using bundle, avoid adding candidates to the wrong
                            // ice transport. And avoid adding candidates added in the SDP.
                            if (sdpMLineIndex === 0 || (sdpMLineIndex > 0 &&
                                transceiver.iceTransport !== pc.transceivers[0].iceTransport)) {
                                if (!maybeAddCandidate(transceiver.iceTransport, cand)) {
                                    return reject(makeError('OperationError',
                                        'Can not add ICE candidate'));
                                }
                            }

                            // update the remoteDescription.
                            var candidateString = candidate.candidate.trim();
                            if (candidateString.indexOf('a=') === 0) {
                                candidateString = candidateString.substr(2);
                            }
                            sections = SDPUtils.getMediaSections(pc._remoteDescription.sdp);
                            sections[sdpMLineIndex] += 'a=' +
                                (cand.type ? candidateString : 'end-of-candidates')
                                + '\r\n';
                            pc._remoteDescription.sdp =
                                SDPUtils.getDescription(pc._remoteDescription.sdp) +
                                sections.join('');
                        } else {
                            return reject(makeError('OperationError',
                                'Can not add ICE candidate'));
                        }
                    }
                    resolve();
                });
            };

            RTCPeerConnection.prototype.getStats = function(selector) {
                if (selector && selector instanceof window.MediaStreamTrack) {
                    var senderOrReceiver = null;
                    this.transceivers.forEach(function(transceiver) {
                        if (transceiver.rtpSender &&
                            transceiver.rtpSender.track === selector) {
                            senderOrReceiver = transceiver.rtpSender;
                        } else if (transceiver.rtpReceiver &&
                            transceiver.rtpReceiver.track === selector) {
                            senderOrReceiver = transceiver.rtpReceiver;
                        }
                    });
                    if (!senderOrReceiver) {
                        throw makeError('InvalidAccessError', 'Invalid selector.');
                    }
                    return senderOrReceiver.getStats();
                }

                var promises = [];
                this.transceivers.forEach(function(transceiver) {
                    ['rtpSender', 'rtpReceiver', 'iceGatherer', 'iceTransport',
                        'dtlsTransport'].forEach(function(method) {
                        if (transceiver[method]) {
                            promises.push(transceiver[method].getStats());
                        }
                    });
                });
                return Promise.all(promises).then(function(allStats) {
                    var results = new Map();
                    allStats.forEach(function(stats) {
                        stats.forEach(function(stat) {
                            results.set(stat.id, stat);
                        });
                    });
                    return results;
                });
            };

            // fix low-level stat names and return Map instead of object.
            var ortcObjects = ['RTCRtpSender', 'RTCRtpReceiver', 'RTCIceGatherer',
                'RTCIceTransport', 'RTCDtlsTransport'];
            ortcObjects.forEach(function(ortcObjectName) {
                var obj = window[ortcObjectName];
                if (obj && obj.prototype && obj.prototype.getStats) {
                    var nativeGetstats = obj.prototype.getStats;
                    obj.prototype.getStats = function() {
                        return nativeGetstats.apply(this)
                            .then(function(nativeStats) {
                                var mapStats = new Map();
                                Object.keys(nativeStats).forEach(function(id) {
                                    nativeStats[id].type = fixStatsType(nativeStats[id]);
                                    mapStats.set(id, nativeStats[id]);
                                });
                                return mapStats;
                            });
                    };
                }
            });

            // legacy callback shims. Should be moved to adapter.js some days.
            var methods = ['createOffer', 'createAnswer'];
            methods.forEach(function(method) {
                var nativeMethod = RTCPeerConnection.prototype[method];
                RTCPeerConnection.prototype[method] = function() {
                    var args = arguments;
                    if (typeof args[0] === 'function' ||
                        typeof args[1] === 'function') { // legacy
                        return nativeMethod.apply(this, [arguments[2]])
                            .then(function(description) {
                                if (typeof args[0] === 'function') {
                                    args[0].apply(null, [description]);
                                }
                            }, function(error) {
                                if (typeof args[1] === 'function') {
                                    args[1].apply(null, [error]);
                                }
                            });
                    }
                    return nativeMethod.apply(this, arguments);
                };
            });

            methods = ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'];
            methods.forEach(function(method) {
                var nativeMethod = RTCPeerConnection.prototype[method];
                RTCPeerConnection.prototype[method] = function() {
                    var args = arguments;
                    if (typeof args[1] === 'function' ||
                        typeof args[2] === 'function') { // legacy
                        return nativeMethod.apply(this, arguments)
                            .then(function() {
                                if (typeof args[1] === 'function') {
                                    args[1].apply(null);
                                }
                            }, function(error) {
                                if (typeof args[2] === 'function') {
                                    args[2].apply(null, [error]);
                                }
                            });
                    }
                    return nativeMethod.apply(this, arguments);
                };
            });

            // getStats is special. It doesn't have a spec legacy method yet we support
            // getStats(something, cb) without error callbacks.
            ['getStats'].forEach(function(method) {
                var nativeMethod = RTCPeerConnection.prototype[method];
                RTCPeerConnection.prototype[method] = function() {
                    var args = arguments;
                    if (typeof args[1] === 'function') {
                        return nativeMethod.apply(this, arguments)
                            .then(function() {
                                if (typeof args[1] === 'function') {
                                    args[1].apply(null);
                                }
                            });
                    }
                    return nativeMethod.apply(this, arguments);
                };
            });

            return RTCPeerConnection;
        };

    },{"sdp":17}],17:[function(require,module,exports){
        /* eslint-env node */
        'use strict';

// SDP helpers.
        var SDPUtils = {};

// Generate an alphanumeric identifier for cname or mids.
// TODO: use UUIDs instead? https://gist.github.com/jed/982883
        SDPUtils.generateIdentifier = function() {
            return Math.random().toString(36).substr(2, 10);
        };

// The RTCP CNAME used by all peerconnections from the same JS.
        SDPUtils.localCName = SDPUtils.generateIdentifier();

// Splits SDP into lines, dealing with both CRLF and LF.
        SDPUtils.splitLines = function(blob) {
            return blob.trim().split('\n').map(function(line) {
                return line.trim();
            });
        };
// Splits SDP into sessionpart and mediasections. Ensures CRLF.
        SDPUtils.splitSections = function(blob) {
            var parts = blob.split('\nm=');
            return parts.map(function(part, index) {
                return (index > 0 ? 'm=' + part : part).trim() + '\r\n';
            });
        };

// returns the session description.
        SDPUtils.getDescription = function(blob) {
            var sections = SDPUtils.splitSections(blob);
            return sections && sections[0];
        };

// returns the individual media sections.
        SDPUtils.getMediaSections = function(blob) {
            var sections = SDPUtils.splitSections(blob);
            sections.shift();
            return sections;
        };

// Returns lines that start with a certain prefix.
        SDPUtils.matchPrefix = function(blob, prefix) {
            return SDPUtils.splitLines(blob).filter(function(line) {
                return line.indexOf(prefix) === 0;
            });
        };

// Parses an ICE candidate line. Sample input:
// candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
// rport 55996"
        SDPUtils.parseCandidate = function(line) {
            var parts;
            // Parse both variants.
            if (line.indexOf('a=candidate:') === 0) {
                parts = line.substring(12).split(' ');
            } else {
                parts = line.substring(10).split(' ');
            }

            var candidate = {
                foundation: parts[0],
                component: parseInt(parts[1], 10),
                protocol: parts[2].toLowerCase(),
                priority: parseInt(parts[3], 10),
                ip: parts[4],
                address: parts[4], // address is an alias for ip.
                port: parseInt(parts[5], 10),
                // skip parts[6] == 'typ'
                type: parts[7]
            };

            for (var i = 8; i < parts.length; i += 2) {
                switch (parts[i]) {
                    case 'raddr':
                        candidate.relatedAddress = parts[i + 1];
                        break;
                    case 'rport':
                        candidate.relatedPort = parseInt(parts[i + 1], 10);
                        break;
                    case 'tcptype':
                        candidate.tcpType = parts[i + 1];
                        break;
                    case 'ufrag':
                        candidate.ufrag = parts[i + 1]; // for backward compability.
                        candidate.usernameFragment = parts[i + 1];
                        break;
                    default: // extension handling, in particular ufrag
                        candidate[parts[i]] = parts[i + 1];
                        break;
                }
            }
            return candidate;
        };

// Translates a candidate object into SDP candidate attribute.
        SDPUtils.writeCandidate = function(candidate) {
            var sdp = [];
            sdp.push(candidate.foundation);
            sdp.push(candidate.component);
            sdp.push(candidate.protocol.toUpperCase());
            sdp.push(candidate.priority);
            sdp.push(candidate.address || candidate.ip);
            sdp.push(candidate.port);

            var type = candidate.type;
            sdp.push('typ');
            sdp.push(type);
            if (type !== 'host' && candidate.relatedAddress &&
                candidate.relatedPort) {
                sdp.push('raddr');
                sdp.push(candidate.relatedAddress);
                sdp.push('rport');
                sdp.push(candidate.relatedPort);
            }
            if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
                sdp.push('tcptype');
                sdp.push(candidate.tcpType);
            }
            if (candidate.usernameFragment || candidate.ufrag) {
                sdp.push('ufrag');
                sdp.push(candidate.usernameFragment || candidate.ufrag);
            }
            return 'candidate:' + sdp.join(' ');
        };

// Parses an ice-options line, returns an array of option tags.
// a=ice-options:foo bar
        SDPUtils.parseIceOptions = function(line) {
            return line.substr(14).split(' ');
        };

// Parses an rtpmap line, returns RTCRtpCoddecParameters. Sample input:
// a=rtpmap:111 opus/48000/2
        SDPUtils.parseRtpMap = function(line) {
            var parts = line.substr(9).split(' ');
            var parsed = {
                payloadType: parseInt(parts.shift(), 10) // was: id
            };

            parts = parts[0].split('/');

            parsed.name = parts[0];
            parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
            parsed.channels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
            // legacy alias, got renamed back to channels in ORTC.
            parsed.numChannels = parsed.channels;
            return parsed;
        };

// Generate an a=rtpmap line from RTCRtpCodecCapability or
// RTCRtpCodecParameters.
        SDPUtils.writeRtpMap = function(codec) {
            var pt = codec.payloadType;
            if (codec.preferredPayloadType !== undefined) {
                pt = codec.preferredPayloadType;
            }
            var channels = codec.channels || codec.numChannels || 1;
            return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
                (channels !== 1 ? '/' + channels : '') + '\r\n';
        };

// Parses an a=extmap line (headerextension from RFC 5285). Sample input:
// a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
// a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
        SDPUtils.parseExtmap = function(line) {
            var parts = line.substr(9).split(' ');
            return {
                id: parseInt(parts[0], 10),
                direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
                uri: parts[1]
            };
        };

// Generates a=extmap line from RTCRtpHeaderExtensionParameters or
// RTCRtpHeaderExtension.
        SDPUtils.writeExtmap = function(headerExtension) {
            return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
                (headerExtension.direction && headerExtension.direction !== 'sendrecv'
                    ? '/' + headerExtension.direction
                    : '') +
                ' ' + headerExtension.uri + '\r\n';
        };

// Parses an ftmp line, returns dictionary. Sample input:
// a=fmtp:96 vbr=on;cng=on
// Also deals with vbr=on; cng=on
        SDPUtils.parseFmtp = function(line) {
            var parsed = {};
            var kv;
            var parts = line.substr(line.indexOf(' ') + 1).split(';');
            for (var j = 0; j < parts.length; j++) {
                kv = parts[j].trim().split('=');
                parsed[kv[0].trim()] = kv[1];
            }
            return parsed;
        };

// Generates an a=ftmp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
        SDPUtils.writeFmtp = function(codec) {
            var line = '';
            var pt = codec.payloadType;
            if (codec.preferredPayloadType !== undefined) {
                pt = codec.preferredPayloadType;
            }
            if (codec.parameters && Object.keys(codec.parameters).length) {
                var params = [];
                Object.keys(codec.parameters).forEach(function(param) {
                    if (codec.parameters[param]) {
                        params.push(param + '=' + codec.parameters[param]);
                    } else {
                        params.push(param);
                    }
                });
                line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
            }
            return line;
        };

// Parses an rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
// a=rtcp-fb:98 nack rpsi
        SDPUtils.parseRtcpFb = function(line) {
            var parts = line.substr(line.indexOf(' ') + 1).split(' ');
            return {
                type: parts.shift(),
                parameter: parts.join(' ')
            };
        };
// Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
        SDPUtils.writeRtcpFb = function(codec) {
            var lines = '';
            var pt = codec.payloadType;
            if (codec.preferredPayloadType !== undefined) {
                pt = codec.preferredPayloadType;
            }
            if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
                // FIXME: special handling for trr-int?
                codec.rtcpFeedback.forEach(function(fb) {
                    lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
                        (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
                        '\r\n';
                });
            }
            return lines;
        };

// Parses an RFC 5576 ssrc media attribute. Sample input:
// a=ssrc:3735928559 cname:something
        SDPUtils.parseSsrcMedia = function(line) {
            var sp = line.indexOf(' ');
            var parts = {
                ssrc: parseInt(line.substr(7, sp - 7), 10)
            };
            var colon = line.indexOf(':', sp);
            if (colon > -1) {
                parts.attribute = line.substr(sp + 1, colon - sp - 1);
                parts.value = line.substr(colon + 1);
            } else {
                parts.attribute = line.substr(sp + 1);
            }
            return parts;
        };

        SDPUtils.parseSsrcGroup = function(line) {
            var parts = line.substr(13).split(' ');
            return {
                semantics: parts.shift(),
                ssrcs: parts.map(function(ssrc) {
                    return parseInt(ssrc, 10);
                })
            };
        };

// Extracts the MID (RFC 5888) from a media section.
// returns the MID or undefined if no mid line was found.
        SDPUtils.getMid = function(mediaSection) {
            var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0];
            if (mid) {
                return mid.substr(6);
            }
        };

        SDPUtils.parseFingerprint = function(line) {
            var parts = line.substr(14).split(' ');
            return {
                algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
                value: parts[1]
            };
        };

// Extracts DTLS parameters from SDP media section or sessionpart.
// FIXME: for consistency with other functions this should only
//   get the fingerprint line as input. See also getIceParameters.
        SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
            var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
                'a=fingerprint:');
            // Note: a=setup line is ignored since we use the 'auto' role.
            // Note2: 'algorithm' is not case sensitive except in Edge.
            return {
                role: 'auto',
                fingerprints: lines.map(SDPUtils.parseFingerprint)
            };
        };

// Serializes DTLS parameters to SDP.
        SDPUtils.writeDtlsParameters = function(params, setupType) {
            var sdp = 'a=setup:' + setupType + '\r\n';
            params.fingerprints.forEach(function(fp) {
                sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
            });
            return sdp;
        };

// Parses a=crypto lines into
//   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#dictionary-rtcsrtpsdesparameters-members
        SDPUtils.parseCryptoLine = function(line) {
            var parts = line.substr(9).split(' ');
            return {
                tag: parseInt(parts[0], 10),
                cryptoSuite: parts[1],
                keyParams: parts[2],
                sessionParams: parts.slice(3),
            };
        };

        SDPUtils.writeCryptoLine = function(parameters) {
            return 'a=crypto:' + parameters.tag + ' ' +
                parameters.cryptoSuite + ' ' +
                (typeof parameters.keyParams === 'object'
                    ? SDPUtils.writeCryptoKeyParams(parameters.keyParams)
                    : parameters.keyParams) +
                (parameters.sessionParams ? ' ' + parameters.sessionParams.join(' ') : '') +
                '\r\n';
        };

// Parses the crypto key parameters into
//   https://rawgit.com/aboba/edgertc/master/msortc-rs4.html#rtcsrtpkeyparam*
        SDPUtils.parseCryptoKeyParams = function(keyParams) {
            if (keyParams.indexOf('inline:') !== 0) {
                return null;
            }
            var parts = keyParams.substr(7).split('|');
            return {
                keyMethod: 'inline',
                keySalt: parts[0],
                lifeTime: parts[1],
                mkiValue: parts[2] ? parts[2].split(':')[0] : undefined,
                mkiLength: parts[2] ? parts[2].split(':')[1] : undefined,
            };
        };

        SDPUtils.writeCryptoKeyParams = function(keyParams) {
            return keyParams.keyMethod + ':'
                + keyParams.keySalt +
                (keyParams.lifeTime ? '|' + keyParams.lifeTime : '') +
                (keyParams.mkiValue && keyParams.mkiLength
                    ? '|' + keyParams.mkiValue + ':' + keyParams.mkiLength
                    : '');
        };

// Extracts all SDES paramters.
        SDPUtils.getCryptoParameters = function(mediaSection, sessionpart) {
            var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
                'a=crypto:');
            return lines.map(SDPUtils.parseCryptoLine);
        };

// Parses ICE information from SDP media section or sessionpart.
// FIXME: for consistency with other functions this should only
//   get the ice-ufrag and ice-pwd lines as input.
        SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
            var ufrag = SDPUtils.matchPrefix(mediaSection + sessionpart,
                'a=ice-ufrag:')[0];
            var pwd = SDPUtils.matchPrefix(mediaSection + sessionpart,
                'a=ice-pwd:')[0];
            if (!(ufrag && pwd)) {
                return null;
            }
            return {
                usernameFragment: ufrag.substr(12),
                password: pwd.substr(10),
            };
        };

// Serializes ICE parameters to SDP.
        SDPUtils.writeIceParameters = function(params) {
            return 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
                'a=ice-pwd:' + params.password + '\r\n';
        };

// Parses the SDP media section and returns RTCRtpParameters.
        SDPUtils.parseRtpParameters = function(mediaSection) {
            var description = {
                codecs: [],
                headerExtensions: [],
                fecMechanisms: [],
                rtcp: []
            };
            var lines = SDPUtils.splitLines(mediaSection);
            var mline = lines[0].split(' ');
            for (var i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
                var pt = mline[i];
                var rtpmapline = SDPUtils.matchPrefix(
                    mediaSection, 'a=rtpmap:' + pt + ' ')[0];
                if (rtpmapline) {
                    var codec = SDPUtils.parseRtpMap(rtpmapline);
                    var fmtps = SDPUtils.matchPrefix(
                        mediaSection, 'a=fmtp:' + pt + ' ');
                    // Only the first a=fmtp:<pt> is considered.
                    codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
                    codec.rtcpFeedback = SDPUtils.matchPrefix(
                        mediaSection, 'a=rtcp-fb:' + pt + ' ')
                        .map(SDPUtils.parseRtcpFb);
                    description.codecs.push(codec);
                    // parse FEC mechanisms from rtpmap lines.
                    switch (codec.name.toUpperCase()) {
                        case 'RED':
                        case 'ULPFEC':
                            description.fecMechanisms.push(codec.name.toUpperCase());
                            break;
                        default: // only RED and ULPFEC are recognized as FEC mechanisms.
                            break;
                    }
                }
            }
            SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function(line) {
                description.headerExtensions.push(SDPUtils.parseExtmap(line));
            });
            // FIXME: parse rtcp.
            return description;
        };

// Generates parts of the SDP media section describing the capabilities /
// parameters.
        SDPUtils.writeRtpDescription = function(kind, caps) {
            var sdp = '';

            // Build the mline.
            sdp += 'm=' + kind + ' ';
            sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
            sdp += ' UDP/TLS/RTP/SAVPF ';
            sdp += caps.codecs.map(function(codec) {
                if (codec.preferredPayloadType !== undefined) {
                    return codec.preferredPayloadType;
                }
                return codec.payloadType;
            }).join(' ') + '\r\n';

            sdp += 'c=IN IP4 0.0.0.0\r\n';
            sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';

            // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
            caps.codecs.forEach(function(codec) {
                sdp += SDPUtils.writeRtpMap(codec);
                sdp += SDPUtils.writeFmtp(codec);
                sdp += SDPUtils.writeRtcpFb(codec);
            });
            var maxptime = 0;
            caps.codecs.forEach(function(codec) {
                if (codec.maxptime > maxptime) {
                    maxptime = codec.maxptime;
                }
            });
            if (maxptime > 0) {
                sdp += 'a=maxptime:' + maxptime + '\r\n';
            }
            sdp += 'a=rtcp-mux\r\n';

            if (caps.headerExtensions) {
                caps.headerExtensions.forEach(function(extension) {
                    sdp += SDPUtils.writeExtmap(extension);
                });
            }
            // FIXME: write fecMechanisms.
            return sdp;
        };

// Parses the SDP media section and returns an array of
// RTCRtpEncodingParameters.
        SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
            var encodingParameters = [];
            var description = SDPUtils.parseRtpParameters(mediaSection);
            var hasRed = description.fecMechanisms.indexOf('RED') !== -1;
            var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;

            // filter a=ssrc:... cname:, ignore PlanB-msid
            var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
                .map(function(line) {
                    return SDPUtils.parseSsrcMedia(line);
                })
                .filter(function(parts) {
                    return parts.attribute === 'cname';
                });
            var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
            var secondarySsrc;

            var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
                .map(function(line) {
                    var parts = line.substr(17).split(' ');
                    return parts.map(function(part) {
                        return parseInt(part, 10);
                    });
                });
            if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
                secondarySsrc = flows[0][1];
            }

            description.codecs.forEach(function(codec) {
                if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
                    var encParam = {
                        ssrc: primarySsrc,
                        codecPayloadType: parseInt(codec.parameters.apt, 10)
                    };
                    if (primarySsrc && secondarySsrc) {
                        encParam.rtx = {ssrc: secondarySsrc};
                    }
                    encodingParameters.push(encParam);
                    if (hasRed) {
                        encParam = JSON.parse(JSON.stringify(encParam));
                        encParam.fec = {
                            ssrc: primarySsrc,
                            mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
                        };
                        encodingParameters.push(encParam);
                    }
                }
            });
            if (encodingParameters.length === 0 && primarySsrc) {
                encodingParameters.push({
                    ssrc: primarySsrc
                });
            }

            // we support both b=AS and b=TIAS but interpret AS as TIAS.
            var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
            if (bandwidth.length) {
                if (bandwidth[0].indexOf('b=TIAS:') === 0) {
                    bandwidth = parseInt(bandwidth[0].substr(7), 10);
                } else if (bandwidth[0].indexOf('b=AS:') === 0) {
                    // use formula from JSEP to convert b=AS to TIAS value.
                    bandwidth = parseInt(bandwidth[0].substr(5), 10) * 1000 * 0.95
                        - (50 * 40 * 8);
                } else {
                    bandwidth = undefined;
                }
                encodingParameters.forEach(function(params) {
                    params.maxBitrate = bandwidth;
                });
            }
            return encodingParameters;
        };

// parses http://draft.ortc.org/#rtcrtcpparameters*
        SDPUtils.parseRtcpParameters = function(mediaSection) {
            var rtcpParameters = {};

            // Gets the first SSRC. Note tha with RTX there might be multiple
            // SSRCs.
            var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
                .map(function(line) {
                    return SDPUtils.parseSsrcMedia(line);
                })
                .filter(function(obj) {
                    return obj.attribute === 'cname';
                })[0];
            if (remoteSsrc) {
                rtcpParameters.cname = remoteSsrc.value;
                rtcpParameters.ssrc = remoteSsrc.ssrc;
            }

            // Edge uses the compound attribute instead of reducedSize
            // compound is !reducedSize
            var rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize');
            rtcpParameters.reducedSize = rsize.length > 0;
            rtcpParameters.compound = rsize.length === 0;

            // parses the rtcp-mux attrіbute.
            // Note that Edge does not support unmuxed RTCP.
            var mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux');
            rtcpParameters.mux = mux.length > 0;

            return rtcpParameters;
        };

// parses either a=msid: or a=ssrc:... msid lines and returns
// the id of the MediaStream and MediaStreamTrack.
        SDPUtils.parseMsid = function(mediaSection) {
            var parts;
            var spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:');
            if (spec.length === 1) {
                parts = spec[0].substr(7).split(' ');
                return {stream: parts[0], track: parts[1]};
            }
            var planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
                .map(function(line) {
                    return SDPUtils.parseSsrcMedia(line);
                })
                .filter(function(msidParts) {
                    return msidParts.attribute === 'msid';
                });
            if (planB.length > 0) {
                parts = planB[0].value.split(' ');
                return {stream: parts[0], track: parts[1]};
            }
        };

// SCTP
// parses draft-ietf-mmusic-sctp-sdp-26 first and falls back
// to draft-ietf-mmusic-sctp-sdp-05
        SDPUtils.parseSctpDescription = function(mediaSection) {
            var mline = SDPUtils.parseMLine(mediaSection);
            var maxSizeLine = SDPUtils.matchPrefix(mediaSection, 'a=max-message-size:');
            var maxMessageSize;
            if (maxSizeLine.length > 0) {
                maxMessageSize = parseInt(maxSizeLine[0].substr(19), 10);
            }
            if (isNaN(maxMessageSize)) {
                maxMessageSize = 65536;
            }
            var sctpPort = SDPUtils.matchPrefix(mediaSection, 'a=sctp-port:');
            if (sctpPort.length > 0) {
                return {
                    port: parseInt(sctpPort[0].substr(12), 10),
                    protocol: mline.fmt,
                    maxMessageSize: maxMessageSize
                };
            }
            var sctpMapLines = SDPUtils.matchPrefix(mediaSection, 'a=sctpmap:');
            if (sctpMapLines.length > 0) {
                var parts = SDPUtils.matchPrefix(mediaSection, 'a=sctpmap:')[0]
                    .substr(10)
                    .split(' ');
                return {
                    port: parseInt(parts[0], 10),
                    protocol: parts[1],
                    maxMessageSize: maxMessageSize
                };
            }
        };

// SCTP
// outputs the draft-ietf-mmusic-sctp-sdp-26 version that all browsers
// support by now receiving in this format, unless we originally parsed
// as the draft-ietf-mmusic-sctp-sdp-05 format (indicated by the m-line
// protocol of DTLS/SCTP -- without UDP/ or TCP/)
        SDPUtils.writeSctpDescription = function(media, sctp) {
            var output = [];
            if (media.protocol !== 'DTLS/SCTP') {
                output = [
                    'm=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.protocol + '\r\n',
                    'c=IN IP4 0.0.0.0\r\n',
                    'a=sctp-port:' + sctp.port + '\r\n'
                ];
            } else {
                output = [
                    'm=' + media.kind + ' 9 ' + media.protocol + ' ' + sctp.port + '\r\n',
                    'c=IN IP4 0.0.0.0\r\n',
                    'a=sctpmap:' + sctp.port + ' ' + sctp.protocol + ' 65535\r\n'
                ];
            }
            if (sctp.maxMessageSize !== undefined) {
                output.push('a=max-message-size:' + sctp.maxMessageSize + '\r\n');
            }
            return output.join('');
        };

// Generate a session ID for SDP.
// https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-20#section-5.2.1
// recommends using a cryptographically random +ve 64-bit value
// but right now this should be acceptable and within the right range
        SDPUtils.generateSessionId = function() {
            return Math.random().toString().substr(2, 21);
        };

// Write boilder plate for start of SDP
// sessId argument is optional - if not supplied it will
// be generated randomly
// sessVersion is optional and defaults to 2
// sessUser is optional and defaults to 'thisisadapterortc'
        SDPUtils.writeSessionBoilerplate = function(sessId, sessVer, sessUser) {
            var sessionId;
            var version = sessVer !== undefined ? sessVer : 2;
            if (sessId) {
                sessionId = sessId;
            } else {
                sessionId = SDPUtils.generateSessionId();
            }
            var user = sessUser || 'thisisadapterortc';
            // FIXME: sess-id should be an NTP timestamp.
            return 'v=0\r\n' +
                'o=' + user + ' ' + sessionId + ' ' + version +
                ' IN IP4 127.0.0.1\r\n' +
                's=-\r\n' +
                't=0 0\r\n';
        };

        SDPUtils.writeMediaSection = function(transceiver, caps, type, stream) {
            var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);

            // Map ICE parameters (ufrag, pwd) to SDP.
            sdp += SDPUtils.writeIceParameters(
                transceiver.iceGatherer.getLocalParameters());

            // Map DTLS parameters to SDP.
            sdp += SDPUtils.writeDtlsParameters(
                transceiver.dtlsTransport.getLocalParameters(),
                type === 'offer' ? 'actpass' : 'active');

            sdp += 'a=mid:' + transceiver.mid + '\r\n';

            if (transceiver.direction) {
                sdp += 'a=' + transceiver.direction + '\r\n';
            } else if (transceiver.rtpSender && transceiver.rtpReceiver) {
                sdp += 'a=sendrecv\r\n';
            } else if (transceiver.rtpSender) {
                sdp += 'a=sendonly\r\n';
            } else if (transceiver.rtpReceiver) {
                sdp += 'a=recvonly\r\n';
            } else {
                sdp += 'a=inactive\r\n';
            }

            if (transceiver.rtpSender) {
                // spec.
                var msid = 'msid:' + stream.id + ' ' +
                    transceiver.rtpSender.track.id + '\r\n';
                sdp += 'a=' + msid;

                // for Chrome.
                sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
                    ' ' + msid;
                if (transceiver.sendEncodingParameters[0].rtx) {
                    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                        ' ' + msid;
                    sdp += 'a=ssrc-group:FID ' +
                        transceiver.sendEncodingParameters[0].ssrc + ' ' +
                        transceiver.sendEncodingParameters[0].rtx.ssrc +
                        '\r\n';
                }
            }
            // FIXME: this should be written by writeRtpDescription.
            sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
                ' cname:' + SDPUtils.localCName + '\r\n';
            if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
                sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                    ' cname:' + SDPUtils.localCName + '\r\n';
            }
            return sdp;
        };

// Gets the direction from the mediaSection or the sessionpart.
        SDPUtils.getDirection = function(mediaSection, sessionpart) {
            // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
            var lines = SDPUtils.splitLines(mediaSection);
            for (var i = 0; i < lines.length; i++) {
                switch (lines[i]) {
                    case 'a=sendrecv':
                    case 'a=sendonly':
                    case 'a=recvonly':
                    case 'a=inactive':
                        return lines[i].substr(2);
                    default:
                    // FIXME: What should happen here?
                }
            }
            if (sessionpart) {
                return SDPUtils.getDirection(sessionpart);
            }
            return 'sendrecv';
        };

        SDPUtils.getKind = function(mediaSection) {
            var lines = SDPUtils.splitLines(mediaSection);
            var mline = lines[0].split(' ');
            return mline[0].substr(2);
        };

        SDPUtils.isRejected = function(mediaSection) {
            return mediaSection.split(' ', 2)[1] === '0';
        };

        SDPUtils.parseMLine = function(mediaSection) {
            var lines = SDPUtils.splitLines(mediaSection);
            var parts = lines[0].substr(2).split(' ');
            return {
                kind: parts[0],
                port: parseInt(parts[1], 10),
                protocol: parts[2],
                fmt: parts.slice(3).join(' ')
            };
        };

        SDPUtils.parseOLine = function(mediaSection) {
            var line = SDPUtils.matchPrefix(mediaSection, 'o=')[0];
            var parts = line.substr(2).split(' ');
            return {
                username: parts[0],
                sessionId: parts[1],
                sessionVersion: parseInt(parts[2], 10),
                netType: parts[3],
                addressType: parts[4],
                address: parts[5]
            };
        };

// a very naive interpretation of a valid SDP.
        SDPUtils.isValidSDP = function(blob) {
            if (typeof blob !== 'string' || blob.length === 0) {
                return false;
            }
            var lines = SDPUtils.splitLines(blob);
            for (var i = 0; i < lines.length; i++) {
                if (lines[i].length < 2 || lines[i].charAt(1) !== '=') {
                    return false;
                }
                // TODO: check the modifier a bit more.
            }
            return true;
        };

// Expose public methods.
        if (typeof module === 'object') {
            module.exports = SDPUtils;
        }

    },{}]},{},[1])(1)
});